# CORE\_DIC

Version: 3.0.11 (2019-09-25)

## <a name="DIFFRACTION"></a>DIFFRACTION

The DICTIONARY group encompassing the CORE DIFFRACTION data items defined
and used with in the Crystallographic Information Framework (CIF).

## <a name="DIFFRN"></a>DIFFRN

The CATEGORY of data items used to describe the diffraction experiment.

### <a name="_diffrn.ambient_environment"></a>\_diffrn.ambient\_environment

The gas or liquid environment of the crystal sample, if not air.

### <a name="_diffrn.ambient_pressure"></a>\_diffrn.ambient\_pressure

Mean hydrostatic  pressure at which intensities were measured.

Units: kilopascals

### <a name="_diffrn.ambient_pressure_gt"></a>\_diffrn.ambient\_pressure\_gt

Mean hydrostatic pressure above which intensities were measured.
These items allow for a pressure range to be given.
    [\_diffrn.ambient\_pressure](#_diffrn.ambient_pressure) should be used in preference to this
item when possible.

Units: kilopascals

### <a name="_diffrn.ambient_pressure_lt"></a>\_diffrn.ambient\_pressure\_lt

Mean hydrostatic pressure below which intensities were measured.
These items allow for a pressure range to be given.
    [\_diffrn.ambient\_pressure](#_diffrn.ambient_pressure) should be used in preference to this
item when possible.

Units: kilopascals

### <a name="_diffrn.ambient_pressure_su"></a>\_diffrn.ambient\_pressure\_su

Standard Uncertainty of the
Mean hydrostatic  pressure at which intensities were measured.

Units: kilopascals

### <a name="_diffrn.ambient_temperature"></a>\_diffrn.ambient\_temperature

Mean temperature at which intensities were measured.

Units: kelvins

### <a name="_diffrn.ambient_temperature_details"></a>\_diffrn.ambient\_temperature\_details

A description of special aspects of temperature control during
data collection.

### <a name="_diffrn.ambient_temperature_gt"></a>\_diffrn.ambient\_temperature\_gt

Mean temperature above which intensities were measured.
These items allow for a temperature range to be given.
    [\_diffrn.ambient\_temperature](#_diffrn.ambient_temperature) should be used in preference to
this item when possible.

Units: kelvins

### <a name="_diffrn.ambient_temperature_lt"></a>\_diffrn.ambient\_temperature\_lt

Mean temperature below which intensities were measured.
These items allow for a temperature range to be given.
    [\_diffrn.ambient\_temperature](#_diffrn.ambient_temperature) should be used in preference to
this item when possible.

Units: kelvins

### <a name="_diffrn.ambient_temperature_su"></a>\_diffrn.ambient\_temperature\_su

Standard Uncertainty of the
mean temperature at which intensities were measured.

Units: kelvins

### <a name="_diffrn.crystal_support"></a>\_diffrn.crystal\_support

The physical device used to support the crystal during data
collection.

### <a name="_diffrn.crystal_treatment"></a>\_diffrn.crystal\_treatment

Remarks about how the crystal was treated prior to intensity measurement.
Particularly relevant when intensities were measured at low temperature.

### <a name="_diffrn.measured_fraction_theta_full"></a>\_diffrn.measured\_fraction\_theta\_full

Fraction of unique (symmetry-independent) reflections measured
out to [\_diffrn\_reflns.theta\_full](#_diffrn_reflns.theta_full).

Units: none

### <a name="_diffrn.measured_fraction_theta_max"></a>\_diffrn.measured\_fraction\_theta\_max

Fraction of unique (symmetry-independent) reflections measured
out to [\_diffrn\_reflns.theta\_max](#_diffrn_reflns.theta_max).

Units: none

### <a name="_diffrn.special_details"></a>\_diffrn.special\_details

Special details of the diffraction measurement process. Should include
information about source instability, crystal motion, degradation, etc.

### <a name="_diffrn.symmetry_description"></a>\_diffrn.symmetry\_description

Recorded diffraction point symmetry, systematic absences and possible
space group(s) or superspace group(s) compatible with these.

## <a name="DIFFRN_ATTENUATOR"></a>DIFFRN\_ATTENUATOR

The CATEGORY of data items which specify the attenuators used in the
diffraction source.

### <a name="_diffrn_attenuator.code"></a>\_diffrn\_attenuator.code

Code identifying a particular attenuator setting; referenced by the
[\_diffrn\_refln.attenuator\_code](#_diffrn_refln.attenuator_code) which is stored with the intensities.

### <a name="_diffrn_attenuator.material"></a>\_diffrn\_attenuator.material

Description of the material from which the attenuator is made.

### <a name="_diffrn_attenuator.scale"></a>\_diffrn\_attenuator.scale

The scale factor applied to a measured intensity if it is reduced by
an attenuator identified by [\_diffrn\_attenuator.code](#_diffrn_attenuator.code).

Units: none

## <a name="DIFFRN_DETECTOR"></a>DIFFRN\_DETECTOR

The CATEGORY of data items which specify the detectors used in the
in the measurement of diffraction intensities.

### <a name="_diffrn_detector.area_resol_mean"></a>\_diffrn\_detector.area\_resol\_mean

The resolution limit of an area diffraction radiation detector.

Units: pixels\_per\_millimetre

### <a name="_diffrn_detector.description"></a>\_diffrn\_detector.description

Description of the type of diffraction radiation detector.

### <a name="_diffrn_detector.details"></a>\_diffrn\_detector.details

Description of special aspects of the radiation detector.

### <a name="_diffrn_detector.dtime"></a>\_diffrn\_detector.dtime

The maximum time between two detector signals that cannot be resolved.

Units: microseconds

### <a name="_diffrn_detector.make"></a>\_diffrn\_detector.make

The make, model or name of the diffraction radiation detector.

## <a name="DIFFRN_MEASUREMENT"></a>DIFFRN\_MEASUREMENT

The CATEGORY of data items which specify the details of the
diffraction measurement.

### <a name="_diffrn_measurement.details"></a>\_diffrn\_measurement.details

Description of special aspects of the diffraction measurement.

### <a name="_diffrn_measurement.device_class"></a>\_diffrn\_measurement.device\_class

Type of goniometer device used to mount and orient the specimen.

### <a name="_diffrn_measurement.device_details"></a>\_diffrn\_measurement.device\_details

Details of the goniometer device used in the diffraction experiment.

### <a name="_diffrn_measurement.device_make"></a>\_diffrn\_measurement.device\_make

The make, model or name of the goniometer device used.

### <a name="_diffrn_measurement.method"></a>\_diffrn\_measurement.method

Description of scan method used to measure diffraction intensities.

### <a name="_diffrn_measurement.specimen_support"></a>\_diffrn\_measurement.specimen\_support

Mounting method for the crystal specimum during data collection.

## <a name="DIFFRN_ORIENT"></a>DIFFRN\_ORIENT

The CATEGORY of data items which specify the orientation of the crystal
axes to the diffractometer goniometer.

## <a name="DIFFRN_ORIENT_MATRIX"></a>DIFFRN\_ORIENT\_MATRIX

The CATEGORY of data items which specify the matrix specifying the
orientation of the crystal axes to the diffractometer goniometer.

### <a name="_diffrn_orient_matrix.type"></a>\_diffrn\_orient\_matrix.type

Description of orientation matrix and how it should be applied to define
the orientation of the crystal with respect to the diffractometer axes.

### <a name="_diffrn_orient_matrix.UB_11"></a>\_diffrn\_orient\_matrix.UB\_11

### <a name="_diffrn_orient_matrix.UB_12"></a>\_diffrn\_orient\_matrix.UB\_12

### <a name="_diffrn_orient_matrix.UB_13"></a>\_diffrn\_orient\_matrix.UB\_13

### <a name="_diffrn_orient_matrix.UB_21"></a>\_diffrn\_orient\_matrix.UB\_21

### <a name="_diffrn_orient_matrix.UB_22"></a>\_diffrn\_orient\_matrix.UB\_22

### <a name="_diffrn_orient_matrix.UB_23"></a>\_diffrn\_orient\_matrix.UB\_23

### <a name="_diffrn_orient_matrix.UB_31"></a>\_diffrn\_orient\_matrix.UB\_31

### <a name="_diffrn_orient_matrix.UB_32"></a>\_diffrn\_orient\_matrix.UB\_32

### <a name="_diffrn_orient_matrix.UB_33"></a>\_diffrn\_orient\_matrix.UB\_33

### <a name="_diffrn_orient_matrix.UBIJ"></a>\_diffrn\_orient\_matrix.UBIJ

The 3x3 matrix specifying the orientation of the crystal with
respect to the diffractometer axes.

## <a name="DIFFRN_ORIENT_REFLN"></a>DIFFRN\_ORIENT\_REFLN

The CATEGORY of data items which specify the reflections used to
calculate the matrix which gives the orientation of the crystal
axes to the diffractometer goniometer.

### <a name="_diffrn_orient_refln.angle_chi"></a>\_diffrn\_orient\_refln.angle\_chi

### <a name="_diffrn_orient_refln.angle_kappa"></a>\_diffrn\_orient\_refln.angle\_kappa

### <a name="_diffrn_orient_refln.angle_omega"></a>\_diffrn\_orient\_refln.angle\_omega

### <a name="_diffrn_orient_refln.angle_phi"></a>\_diffrn\_orient\_refln.angle\_phi

### <a name="_diffrn_orient_refln.angle_psi"></a>\_diffrn\_orient\_refln.angle\_psi

### <a name="_diffrn_orient_refln.angle_theta"></a>\_diffrn\_orient\_refln.angle\_theta

### <a name="_diffrn_orient_refln.hkl"></a>\_diffrn\_orient\_refln.hkl

Miller indices of a reflection used to define the orientation matrix.

### <a name="_diffrn_orient_refln.index_h"></a>\_diffrn\_orient\_refln.index\_h

### <a name="_diffrn_orient_refln.index_k"></a>\_diffrn\_orient\_refln.index\_k

### <a name="_diffrn_orient_refln.index_l"></a>\_diffrn\_orient\_refln.index\_l

## <a name="DIFFRN_RADIATION"></a>DIFFRN\_RADIATION

The CATEGORY of data items which specify the wavelength of the
radiation used in measuring diffraction intensities. Items may be
looped to identify and assign weights to distinct wavelength
components from a polychromatic beam.

### <a name="_diffrn_radiation.collimation"></a>\_diffrn\_radiation.collimation

Description of the collimation or focusing applied to the radiation.

### <a name="_diffrn_radiation.filter_edge"></a>\_diffrn\_radiation.filter\_edge

Absorption edge of the radiation filter used.

Units: angstroms

### <a name="_diffrn_radiation.inhomogeneity"></a>\_diffrn\_radiation.inhomogeneity

Half-width of the incident beam perpendicular to the diffraction plane.

Units: millimetres

### <a name="_diffrn_radiation.monochromator"></a>\_diffrn\_radiation.monochromator

Description of the method used to obtain monochromatic radiation.
If a monochromator crystal is used the material and the indices of
the Bragg reflection are specified.

### <a name="_diffrn_radiation.polarisn_norm"></a>\_diffrn\_radiation.polarisn\_norm

The angle, as viewed from the specimen, between the perpendicular
component of the polarisation and the diffraction plane.

Units: degrees

### <a name="_diffrn_radiation.polarisn_ratio"></a>\_diffrn\_radiation.polarisn\_ratio

Polarisation ratio of the diffraction beam incident on the crystal.
It is the ratio of the perpendicularly polarised to the parallel
polarised component of the radiation. The perpendicular component
forms an angle of [\_diffrn\_radiation.polarisn\_norm](#_diffrn_radiation.polarisn_norm) to the normal to
the diffraction plane of the sample (i.e. the plane containing the
incident and reflected beams).

Units: none

### <a name="_diffrn_radiation.probe"></a>\_diffrn\_radiation.probe

Enumerated code for the nature of radiation used (i.e. name of
subatomic particle or region of the electromagnetic spectrum).

Values:

* x-ray
* neutron
* electron
* gamma

### <a name="_diffrn_radiation.type"></a>\_diffrn\_radiation.type

Details of the radiation source or energy spectrum.

### <a name="_diffrn_radiation.xray_symbol"></a>\_diffrn\_radiation.xray\_symbol

IUPAC symbol for the X-ray wavelength for probe radiation.

Values:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>K-L~3~</td><td>K\a~1~ in older Siegbahn notation</td></tr>
  <tr><td>K-L~2~</td><td>K\a~2~ in older Siegbahn notation</td></tr>
  <tr><td>K-M~3~</td><td>K\b~1~ in older Siegbahn notation</td></tr>
  <tr><td>K-L~2,3~</td><td>use where K-L~3~ and K-L~2~ are not resolved</td></tr>
</table>
## <a name="DIFFRN_RADIATION_WAVELENGTH"></a>DIFFRN\_RADIATION\_WAVELENGTH

The CATEGORY of data items which specify the wavelength of the
radiation used in measuring diffraction intensities. Items may be
looped to identify and assign weights to distinct wavelength
components from a polychromatic beam.

### <a name="_diffrn_radiation_wavelength.details"></a>\_diffrn\_radiation\_wavelength.details

Information about the determination of the radiation
diffrn\_radiation\_wavelength that is not conveyed completely by an
enumerated value of [\_diffrn\_radiation\_wavelength.determination](#_diffrn_radiation_wavelength.determination).

### <a name="_diffrn_radiation_wavelength.determination"></a>\_diffrn\_radiation\_wavelength.determination

Method by which the radiation wavelength was determined.

Values:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>fundamental</td><td>Fundamental property of matter e.g. MoK\alpha</td></tr>
  <tr><td>estimated</td><td>Estimated  e.g. from monochromator angle or time of flight</td></tr>
  <tr><td>refined</td><td>Refined using a standard crystal with known cell parameters</td></tr>
</table>
### <a name="_diffrn_radiation_wavelength.id"></a>\_diffrn\_radiation\_wavelength.id

Code identifying a radiation used in the diffraction measurements.
This is linked to [\_diffrn\_refln.wavelength\_id](#_diffrn_refln.wavelength_id) and [\_refln.wavelength\_id](#_refln.wavelength_id)

### <a name="_diffrn_radiation_wavelength.value"></a>\_diffrn\_radiation\_wavelength.value

Wavelength of radiation used in diffraction measurements.

Units: angstroms

### <a name="_diffrn_radiation_wavelength.value_su"></a>\_diffrn\_radiation\_wavelength.value\_su

Standard uncertainty of the wavelength of radiation used in diffraction
measurements.

Units: none

### <a name="_diffrn_radiation_wavelength.wt"></a>\_diffrn\_radiation\_wavelength.wt

Relative intensity of a radiation used in the diffraction measurements.

Units: none

## <a name="DIFFRN_REFLN"></a>DIFFRN\_REFLN

The CATEGORY of data items which specify the reflection measurements,
prior to data reduction and merging.

### <a name="_diffrn_refln.angle_chi"></a>\_diffrn\_refln.angle\_chi

### <a name="_diffrn_refln.angle_kappa"></a>\_diffrn\_refln.angle\_kappa

### <a name="_diffrn_refln.angle_omega"></a>\_diffrn\_refln.angle\_omega

### <a name="_diffrn_refln.angle_phi"></a>\_diffrn\_refln.angle\_phi

### <a name="_diffrn_refln.angle_psi"></a>\_diffrn\_refln.angle\_psi

### <a name="_diffrn_refln.angle_theta"></a>\_diffrn\_refln.angle\_theta

### <a name="_diffrn_refln.attenuator_code"></a>\_diffrn\_refln.attenuator\_code

Code identifying any attenuator setting for this reflection.

### <a name="_diffrn_refln.class_code"></a>\_diffrn\_refln.class\_code

Code for reflection class, if assigned. e.g. modulated structures

### <a name="_diffrn_refln.counts_bg_1"></a>\_diffrn\_refln.counts\_bg\_1

### <a name="_diffrn_refln.counts_bg_2"></a>\_diffrn\_refln.counts\_bg\_2

### <a name="_diffrn_refln.counts_net"></a>\_diffrn\_refln.counts\_net

### <a name="_diffrn_refln.counts_peak"></a>\_diffrn\_refln.counts\_peak

### <a name="_diffrn_refln.counts_total"></a>\_diffrn\_refln.counts\_total

### <a name="_diffrn_refln.detect_slit_horiz"></a>\_diffrn\_refln.detect\_slit\_horiz

Total slit aperture angle in the diffraction plane.

Units: degrees

### <a name="_diffrn_refln.detect_slit_vert"></a>\_diffrn\_refln.detect\_slit\_vert

Total slit aperture angle perpendicular to the diffraction plane.

Units: degrees

### <a name="_diffrn_refln.elapsed_time"></a>\_diffrn\_refln.elapsed\_time

Elapsed time from the start to the end of the intensity measurement.

Units: minutes

### <a name="_diffrn_refln.hkl"></a>\_diffrn\_refln.hkl

Miller indices of a measured reflection. These need not match the
[\_refln.hkl](#_refln.hkl) values if a transformation of the original measured
cell has taken place.

### <a name="_diffrn_refln.index_h"></a>\_diffrn\_refln.index\_h

### <a name="_diffrn_refln.index_k"></a>\_diffrn\_refln.index\_k

### <a name="_diffrn_refln.index_l"></a>\_diffrn\_refln.index\_l

### <a name="_diffrn_refln.intensity_net"></a>\_diffrn\_refln.intensity\_net

Net intensity calculated from the diffraction counts after the
attenuator and standard scales have been applied.

Units: none

### <a name="_diffrn_refln.intensity_net_su"></a>\_diffrn\_refln.intensity\_net\_su

Standard uncertainty of the net intensity calculated from the
diffraction counts after the attenuator and standard scales
have been applied.

Units: none

### <a name="_diffrn_refln.scale_group_code"></a>\_diffrn\_refln.scale\_group\_code

Code identifying the scale applying to this reflection.

### <a name="_diffrn_refln.scan_mode"></a>\_diffrn\_refln.scan\_mode

Code identifying the mode of scanning with a diffractometer.
See also  [\_diffrn\_refln.scan\_width](#_diffrn_refln.scan_width) and [\_diffrn\_refln.scan\_mode\_backgd](#_diffrn_refln.scan_mode_backgd).

Values:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>om</td><td>omega scan</td></tr>
  <tr><td>ot</td><td>omega/2theta scan</td></tr>
  <tr><td>q</td><td>Q-scans (arbitrary reciprocal directions)</td></tr>
</table>
### <a name="_diffrn_refln.scan_mode_backgd"></a>\_diffrn\_refln.scan\_mode\_backgd

Code identifying mode of scanning to measure the background intensity.

Values:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>st</td><td>stationary counter background</td></tr>
  <tr><td>mo</td><td>moving counter background</td></tr>
</table>
### <a name="_diffrn_refln.scan_rate"></a>\_diffrn\_refln.scan\_rate

Angular rate of scanning a reflection to measure the intensity.

Units: degree\_per\_minute

### <a name="_diffrn_refln.scan_time_backgd"></a>\_diffrn\_refln.scan\_time\_backgd

Time spent measuring background counts.

Units: seconds

### <a name="_diffrn_refln.scan_width"></a>\_diffrn\_refln.scan\_width

Angular scan width when measuring the peak intensity.

Units: degrees

### <a name="_diffrn_refln.sin_theta_over_lambda"></a>\_diffrn\_refln.sin\_theta\_over\_lambda

(sin theta)/lambda value for this reflection.

Units: reciprocal\_angstroms

### <a name="_diffrn_refln.standard_code"></a>\_diffrn\_refln.standard\_code

Code identifying reflections measured repeated as standard intensity.
Must match a [\_diffrn\_standard\_refln.code](#_diffrn_standard_refln.code) values OR set to &#39;.&#39; if
it was not used as a intensity standard.

### <a name="_diffrn_refln.wavelength"></a>\_diffrn\_refln.wavelength

Mean wavelength of radiation used to measure this intensity.

Units: angstroms

### <a name="_diffrn_refln.wavelength_id"></a>\_diffrn\_refln.wavelength\_id

Code identifying the wavelength in the diffrn\_radiation\_wavelength list.

## <a name="DIFFRN_REFLNS"></a>DIFFRN\_REFLNS

The CATEGORY of data items which specify the overall reflection
measurement information.

### <a name="_diffrn_reflns.av_R_equivalents"></a>\_diffrn\_reflns.av\_R\_equivalents

The residual [sum av|del(I)| / sum |av(I)|] for symmetry-equivalent
reflections used to calculate the average intensity av(I). The
av|del(I)| term is the average absolute difference between av(I) and
the individual symmetry-equivalent intensities.

Units: none

### <a name="_diffrn_reflns.av_sunetI_over_netI"></a>\_diffrn\_reflns.av\_sunetI\_over\_netI

Recorded [sum |su(netI)| / sum |netI|] for all measured reflections.

Units: none

### <a name="_diffrn_reflns.Laue_measured_fraction_full"></a>\_diffrn\_reflns.Laue\_measured\_fraction\_full

Fraction of Laue group unique reflections (symmetry-independent in
the Laue group) measured out to the resolution given in
[\_diffrn\_reflns.resolution\_full](#_diffrn_reflns.resolution_full) or [\_diffrn\_reflns.theta\_full](#_diffrn_reflns.theta_full).
The Laue group always contains a centre of symmetry so that
the reflection h,k,l is always equivalent to the reflection
-h,-k,-l even in space groups without a centre of symmetry.
This number should not be less than 0.95, since it represents
the fraction of reflections measured in the part of the
diffraction pattern that is essentially complete.

Units: none

### <a name="_diffrn_reflns.Laue_measured_fraction_max"></a>\_diffrn\_reflns.Laue\_measured\_fraction\_max

Fraction of Laue-group unique reflections (symmetry-independent in
the Laue group) measured out to the resolution given in
[\_diffrn\_reflns.resolution\_max](#_diffrn_reflns.resolution_max) or [\_diffrn\_reflns.theta\_max](#_diffrn_reflns.theta_max).
The Laue group always contains a centre of symmetry so that the
reflection h,k,l is always equivalent to the reflection -h,-k,-l
even in space groups without a centre of symmetry.

Units: none

### <a name="_diffrn_reflns.limit_h_max"></a>\_diffrn\_reflns.limit\_h\_max

### <a name="_diffrn_reflns.limit_h_min"></a>\_diffrn\_reflns.limit\_h\_min

### <a name="_diffrn_reflns.limit_k_max"></a>\_diffrn\_reflns.limit\_k\_max

### <a name="_diffrn_reflns.limit_k_min"></a>\_diffrn\_reflns.limit\_k\_min

### <a name="_diffrn_reflns.limit_l_max"></a>\_diffrn\_reflns.limit\_l\_max

### <a name="_diffrn_reflns.limit_l_min"></a>\_diffrn\_reflns.limit\_l\_min

### <a name="_diffrn_reflns.limit_max"></a>\_diffrn\_reflns.limit\_max

Maximum Miller indices of measured diffraction reflections.

### <a name="_diffrn_reflns.limit_min"></a>\_diffrn\_reflns.limit\_min

Minimum Miller indices of meas.ued diffraction reflections.

### <a name="_diffrn_reflns.number"></a>\_diffrn\_reflns.number

Total number of measured intensities, excluding reflections that are
classed as systematically absent arising from translational symmetry
in the crystal unit cell.

### <a name="_diffrn_reflns.point_measured_fraction_full"></a>\_diffrn\_reflns.point\_measured\_fraction\_full

Fraction of crystal point-group unique reflections (i.e.
symmetry-independent in the crystal point group) measured
out to the resolution given in [\_diffrn\_reflns.resolution\_full](#_diffrn_reflns.resolution_full)
or [\_diffrn\_reflns.theta\_full](#_diffrn_reflns.theta_full). For space groups that do not
contain a centre of symmetry the reflections h,k,l and
-h,-k,-l are independent. This number should not be less
than 0.95, since it represents the fraction of reflections
measured in the part of the diffraction pattern that is
essentially complete.

Units: none

### <a name="_diffrn_reflns.point_measured_fraction_max"></a>\_diffrn\_reflns.point\_measured\_fraction\_max

Fraction of crystal point-group unique reflections (i.e.
symmetry-independent in the crystal point group) measured
out to the resolution given in [\_diffrn\_reflns.resolution\_max](#_diffrn_reflns.resolution_max)
or [\_diffrn\_reflns.theta\_max](#_diffrn_reflns.theta_max). For space groups that do not
contain a centre of symmetry the reflections h,k,l and
-h,-k,-l are independent.

Units: none

### <a name="_diffrn_reflns.reduction_process"></a>\_diffrn\_reflns.reduction\_process

How intensities were reduced to structure-factor magnitudes.

### <a name="_diffrn_reflns.resolution_full"></a>\_diffrn\_reflns.resolution\_full

The resolution at which the measured reflection count is close
to complete. The fraction of unique reflections measured out
to this angle is given by [\_diffrn.measured\_fraction\_theta\_full](#_diffrn.measured_fraction_theta_full).

Units: reciprocal\_angstroms

### <a name="_diffrn_reflns.resolution_max"></a>\_diffrn\_reflns.resolution\_max

Maximum resolution of the measured diffraction pattern.
The fraction of unique reflections measured out to this angle
is given by [\_diffrn.measured\_fraction\_theta\_max](#_diffrn.measured_fraction_theta_max).

Units: reciprocal\_angstroms

### <a name="_diffrn_reflns.theta_full"></a>\_diffrn\_reflns.theta\_full

Theta angle at which the count of measured reflections is almost
complete.  The fraction of unique reflections measured out to
this angle is given by [\_diffrn.measured\_fraction\_theta\_full](#_diffrn.measured_fraction_theta_full).

Units: degrees

### <a name="_diffrn_reflns.theta_max"></a>\_diffrn\_reflns.theta\_max

Maximum theta angle of the measured reflections.

Units: degrees

### <a name="_diffrn_reflns.theta_min"></a>\_diffrn\_reflns.theta\_min

Minimum theta angle of the measured reflections.

Units: degrees

## <a name="DIFFRN_REFLNS_CLASS"></a>DIFFRN\_REFLNS\_CLASS

The CATEGORY of data items which specify different classes of
reflections in the raw measured diffraction data.
 

### <a name="_diffrn_reflns_class.av_R_eq"></a>\_diffrn\_reflns\_class.av\_R\_eq

Residual [sum av|del(I)|/sum|av(I)|] for symmetry-equivalent
reflections used to calculate the average intensity av(I).
The av|del(I)| term is the average absolute difference
between av(I) and the individual intensities.

Units: none

### <a name="_diffrn_reflns_class.av_suI_over_I"></a>\_diffrn\_reflns\_class.av\_suI\_over\_I

Recorded [sum|su(net I)|/sum|net I|] in a reflection class.

Units: none

### <a name="_diffrn_reflns_class.code"></a>\_diffrn\_reflns\_class.code

Code identifying a reflection class.

### <a name="_diffrn_reflns_class.d_res_high"></a>\_diffrn\_reflns\_class.d\_res\_high

Highest resolution in reflection class i.e. smallest d value in class.

Units: angstroms

### <a name="_diffrn_reflns_class.d_res_low"></a>\_diffrn\_reflns\_class.d\_res\_low

Lowest resolution in reflection class i.e. largest d value in class.

Units: angstroms

### <a name="_diffrn_reflns_class.description"></a>\_diffrn\_reflns\_class.description

Description of a reflection class.

### <a name="_diffrn_reflns_class.number"></a>\_diffrn\_reflns\_class.number

Number of measured intensities for a reflection class, excluding
the systematic absences arising from centring translations.

## <a name="DIFFRN_REFLNS_TRANSF_MATRIX"></a>DIFFRN\_REFLNS\_TRANSF\_MATRIX

The CATEGORY of data items which specify the elements of the matrix
used to transform the reflection indices [\_diffrn\_refln.hkl](#_diffrn_refln.hkl)
into [\_refln.hkl](#_refln.hkl).
                            |11 12 13|
       (h k l) diffraction  |21 22 23|  =  (h&#39; k&#39; l&#39;)
                            |31 32 33|

### <a name="_diffrn_reflns_transf_matrix.11"></a>\_diffrn\_reflns\_transf\_matrix.11

### <a name="_diffrn_reflns_transf_matrix.12"></a>\_diffrn\_reflns\_transf\_matrix.12

### <a name="_diffrn_reflns_transf_matrix.13"></a>\_diffrn\_reflns\_transf\_matrix.13

### <a name="_diffrn_reflns_transf_matrix.21"></a>\_diffrn\_reflns\_transf\_matrix.21

### <a name="_diffrn_reflns_transf_matrix.22"></a>\_diffrn\_reflns\_transf\_matrix.22

### <a name="_diffrn_reflns_transf_matrix.23"></a>\_diffrn\_reflns\_transf\_matrix.23

### <a name="_diffrn_reflns_transf_matrix.31"></a>\_diffrn\_reflns\_transf\_matrix.31

### <a name="_diffrn_reflns_transf_matrix.32"></a>\_diffrn\_reflns\_transf\_matrix.32

### <a name="_diffrn_reflns_transf_matrix.33"></a>\_diffrn\_reflns\_transf\_matrix.33

### <a name="_diffrn_reflns_transf_matrix.TIJ"></a>\_diffrn\_reflns\_transf\_matrix.TIJ

Elements of the matrix used to transform the diffraction reflection
indices [\_diffrn\_refln.hkl](#_diffrn_refln.hkl) into the [\_refln.hkl](#_refln.hkl) indices.
                             |11 12 13|
        (h k l) diffraction  |21 22 23|  =  (h&#39; k&#39; l&#39;)
                             |31 32 33|

## <a name="DIFFRN_SCALE_GROUP"></a>DIFFRN\_SCALE\_GROUP

The CATEGORY of data items which specify the groups of reflections in
the raw measured diffraction data with different relative scales.

### <a name="_diffrn_scale_group.code"></a>\_diffrn\_scale\_group.code

Code identifying a specific scale group of reflections (e.g. for
multi-film or multi-crystal data). The code must match a
[\_diffrn\_refln.scale\_group\_code](#_diffrn_refln.scale_group_code) in the [DIFFRN\_REFLN](#DIFFRN_REFLN) list.

### <a name="_diffrn_scale_group.I_net"></a>\_diffrn\_scale\_group.I\_net

Scale for a specific measurement group of eflections. Is multiplied
with the net intensity to place all intensities on a common scale.

Units: none

## <a name="DIFFRN_SOURCE"></a>DIFFRN\_SOURCE

The CATEGORY of data items which specify information about the
radiation source.

### <a name="_diffrn_source.current"></a>\_diffrn\_source.current

Generator current at which the radiation source device was operated.

Units: milliamperes

### <a name="_diffrn_source.description"></a>\_diffrn\_source.description

The general class of the source of radiation. This is deprecated.
Use [\_diffrn\_source.device](#_diffrn_source.device) and [\_diffrn\_source.details](#_diffrn_source.details).

### <a name="_diffrn_source.details"></a>\_diffrn\_source.details

A description of special aspects of the source.

### <a name="_diffrn_source.device"></a>\_diffrn\_source.device

Enumerated code for the device providing the source of radiation.

Values:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>tube</td><td>sealed X-ray tube</td></tr>
  <tr><td>nuclear</td><td>nuclear reactor</td></tr>
  <tr><td>spallation</td><td>spallation source</td></tr>
  <tr><td>elect-micro</td><td>electron microscope</td></tr>
  <tr><td>rot_anode</td><td>rotating-anode X-ray tube</td></tr>
  <tr><td>synch</td><td>synchrotron</td></tr>
</table>
### <a name="_diffrn_source.make"></a>\_diffrn\_source.make

Description of the make, model or name of the source device.

### <a name="_diffrn_source.power"></a>\_diffrn\_source.power

Generator power at which the radiation source device was operated.

Units: kilowatts

### <a name="_diffrn_source.size"></a>\_diffrn\_source.size

Description of the collimated source beam as viewed from the sample.

### <a name="_diffrn_source.take_off_angle"></a>\_diffrn\_source.take\_off\_angle

The complement of the angle in degrees between the normal
to the surface of the X-ray tube target and the primary
X-ray beam for beams generated by traditional X-ray tubes.

Units: degrees

### <a name="_diffrn_source.target"></a>\_diffrn\_source.target

Chemical element symbol for the radiation source target (usually
the anode). This can be used also for spallation sources.

### <a name="_diffrn_source.voltage"></a>\_diffrn\_source.voltage

Generator voltage at which the radiation source device was operated.

Units: kilovolts

## <a name="DIFFRN_STANDARD"></a>DIFFRN\_STANDARD

The CATEGORY of data items which specify information about the
standard reflections used in the diffraction measurement process.

### <a name="_diffrn_standard.decay_percent"></a>\_diffrn\_standard.decay\_percent

The percentage decrease in the mean of the intensities for the
standard reflections at the start to the finish of the measurement
process. This value affords a measure of the overall decay in
crystal quality during measurement. Negative values only occur in
exceptional instances where the final intensities are greater than
the initial ones.  If no measurable decay has occurred, the
standard uncertainty should be quoted to indicate the maximum
possible value the decay might have.  A range of 3 standard
uncertainties is considered possible.  Thus 0.0(1) would indicate
a decay of less than 0.3% or an enhancement of less than 0.3%.

Units: none

Examples:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>
0.5(1)
  </td><td>represents a decay between 0.2% and 0.8%
  </td></tr>
  <tr><td>
-1(1)
  </td><td>change in standards between 2% decay and 4% rise
  </td></tr>
  <tr><td>
0.0(2)
  </td><td>change in standards between 0.6% decay and 0.6% rise.
  </td></tr>
</table>
### <a name="_diffrn_standard.interval_count"></a>\_diffrn\_standard.interval\_count

Reflection count between the standard reflection measurements.

### <a name="_diffrn_standard.interval_time"></a>\_diffrn\_standard.interval\_time

Time between the standard reflection measurements.

Units: minutes

### <a name="_diffrn_standard.number"></a>\_diffrn\_standard.number

Number of unique standard reflections used in measurements.

### <a name="_diffrn_standard.scale_su_average"></a>\_diffrn\_standard.scale\_su\_average

The average standard uncertainty of the individual standard scales
applied to the intensity data.

Units: none

## <a name="DIFFRN_STANDARD_REFLN"></a>DIFFRN\_STANDARD\_REFLN

The CATEGORY of data items which specify the &quot;standard&quot; reflections
measured repeatedly to monitor variations in intensity due to source
flux, environment conditions or crystal quality.

### <a name="_diffrn_standard_refln.code"></a>\_diffrn\_standard\_refln.code

Code identifying a standard reflection used to monitor source
intensity variations or crystal degradation or movement during
data collection.

### <a name="_diffrn_standard_refln.hkl"></a>\_diffrn\_standard\_refln.hkl

Miller indices of a standard reflection.

### <a name="_diffrn_standard_refln.index_h"></a>\_diffrn\_standard\_refln.index\_h

### <a name="_diffrn_standard_refln.index_k"></a>\_diffrn\_standard\_refln.index\_k

### <a name="_diffrn_standard_refln.index_l"></a>\_diffrn\_standard\_refln.index\_l

## <a name="REFLN"></a>REFLN

The CATEGORY of data items used to describe the reflection data
used in the refinement of a crystallographic structure model.

### <a name="_refln.A_calc"></a>\_refln.A\_calc

The calculated real structure-factor component A =|Fcalc|cos(phase)

### <a name="_refln.A_meas"></a>\_refln.A\_meas

The measured real structure-factor component A =|Fmeas|cos(phase)

### <a name="_refln.B_calc"></a>\_refln.B\_calc

The calculated imaginary structure-factor component B =|Fcalc|sin(phase)

### <a name="_refln.B_meas"></a>\_refln.B\_meas

The measured imaginary structure-factor component B =|Fmeas|sin(phase)

### <a name="_refln.class_code"></a>\_refln.class\_code

Code identifying the class to which this reflection has been
assigned. This code must match a value of [\_reflns\_class.code](#_reflns_class.code).
Reflections may be grouped into classes for a variety of
purposes. For example, for modulated structures each reflection
class may be defined by the number m=sum|m~i~|, where the m~i~
are the integer coefficients that, in addition to h,k,l, index
the corresponding diffraction vector in the basis defined
for the reciprocal lattice.

### <a name="_refln.d_spacing"></a>\_refln.d\_spacing

The distance in angstroms between lattice planes in the crystal
with the indices [\_refln.hkl](#_refln.hkl) for this reflection.

Units: angstroms

### <a name="_refln.F_calc"></a>\_refln.F\_calc

The structure factor amplitude for the reflection calculated from
the atom site data.

### <a name="_refln.F_complex"></a>\_refln.F\_complex

The structure factor vector for the reflection calculated from
the atom site data.

### <a name="_refln.F_meas"></a>\_refln.F\_meas

The structure factor amplitude for the reflection derived from the
measured intensities.

### <a name="_refln.F_meas_su"></a>\_refln.F\_meas\_su

The standard uncertainty of the measured structure factor amplitude.

### <a name="_refln.F_squared_calc"></a>\_refln.F\_squared\_calc

The structure factor amplitude squared for the reflection calculated from
the atom site data.

### <a name="_refln.F_squared_meas"></a>\_refln.F\_squared\_meas

The structure factor amplitude for the reflection derived from the
measured intensities.

### <a name="_refln.F_squared_meas_su"></a>\_refln.F\_squared\_meas\_su

The standard uncertainty of the measured structure factor squared.

### <a name="_refln.fom"></a>\_refln.fom

The figure of merit m for this reflection.
 
    int P~alpha~ exp(i\*alpha) dalpha
m = --------------------------------
          int P~alpha~ dalpha
 
P~a~ = the probability that the phase angle a is correct
 
int is taken over the range alpha = 0 to 2 pi.

### <a name="_refln.form_factor_table"></a>\_refln.form\_factor\_table

Atomic scattering factor table for the scattering angle
of this diffraction vector and atom types in structure.

Units: none

### <a name="_refln.hkl"></a>\_refln.hkl

The Miller indices as a reciprocal space vector.

### <a name="_refln.include_status"></a>\_refln.include\_status

Code indicating how the reflection was included in the refinement
and R-factor calculations.

Values:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>o</td><td>ob : within  _reflns.threshold_expression; within d-res limits</td></tr>
  <tr><td>&lt;</td><td>lt : without _reflns.threshold_expression; within d-res limits</td></tr>
  <tr><td>-</td><td>sa : systematically absent reflection due to symmetry</td></tr>
  <tr><td>x</td><td>du : deemed unreliable measurement -- not used</td></tr>
  <tr><td>h</td><td>hd : above _refine_ls.d_res_high</td></tr>
  <tr><td>l</td><td>ld : below _refine_ls.d_res_low</td></tr>
</table>
### <a name="_refln.index_h"></a>\_refln.index\_h

### <a name="_refln.index_k"></a>\_refln.index\_k

### <a name="_refln.index_l"></a>\_refln.index\_l

### <a name="_refln.intensity_calc"></a>\_refln.intensity\_calc

The intensity of the reflection calculated from the atom site data.

Units: none

### <a name="_refln.intensity_meas"></a>\_refln.intensity\_meas

The intensity of the reflection derived from the diffraction measurements.

Units: none

### <a name="_refln.intensity_meas_su"></a>\_refln.intensity\_meas\_su

standard uncertainty of the measured intensity.

Units: none

### <a name="_refln.Lp_factor"></a>\_refln.Lp\_factor

The Lorentz-polarization factor appropriate for the instrument
used to measure the diffraction intensity. This is applied to
convert the net intensity into the measured F squared.

Units: none

### <a name="_refln.mean_path_length_tbar"></a>\_refln.mean\_path\_length\_tbar

Mean path length through the crystal for this diffraction vector.

Units: millimetres

### <a name="_refln.phase_calc"></a>\_refln.phase\_calc

The phase of the calculated structure-factor.

Units: degrees

### <a name="_refln.phase_meas"></a>\_refln.phase\_meas

The phase of the measured structure-factor. This may be derived from
the atom site data if available or from the phase solution process
prior to determination of the structure.

Units: degrees

### <a name="_refln.refinement_status"></a>\_refln.refinement\_status

Status code of reflection in the structure refinement process.

Values:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>incl</td><td>included in ls process</td></tr>
  <tr><td>excl</td><td>excluded from ls process</td></tr>
  <tr><td>extn</td><td>excluded due to extinction</td></tr>
</table>
### <a name="_refln.scale_group_code"></a>\_refln.scale\_group\_code

Code identifying the scale (if there is more than one scale) used
convert the measured structure factor to a common absolute value.

### <a name="_refln.sin_theta_over_lambda"></a>\_refln.sin\_theta\_over\_lambda

The (sin theta)/lambda value for this reflection.

Units: reciprocal\_angstroms

### <a name="_refln.symmetry_epsilon"></a>\_refln.symmetry\_epsilon

The symmetry reinforcement factor corresponding to the number of
times the reflection indices are generated identically from the
space-group symmetry operations.

### <a name="_refln.symmetry_multiplicity"></a>\_refln.symmetry\_multiplicity

The number of reflections symmetry-equivalent under the Laue
symmetry to the present reflection. In the Laue symmetry, Friedel
opposites (h k l and -h -k -l) are equivalent. Tables of
symmetry-equivalent reflections are available in International
Tables for Crystallography, Volume A (1987), section 10.2.

### <a name="_refln.wavelength"></a>\_refln.wavelength

The mean wavelength in angstroms of radiation used to measure
this reflection. This is an important parameter for data
collected using energy-dispersive detectors or the Laue method.

Units: angstroms

### <a name="_refln.wavelength_id"></a>\_refln.wavelength\_id

Code identifying the wavelength in [DIFFRN\_RADIATION\_WAVELENGTH](#DIFFRN_RADIATION_WAVELENGTH) list.

## <a name="REFLNS"></a>REFLNS

The CATEGORY of data items used to specify parameters for the complete
set of reflections used in the structure refinement process. Note that
these parameters are often similar measures to those defined in the
DIFFRN categories, but differ in that the parameters refer to the
reduced/transformed reflections which have been used to refine the
atom site data in the [ATOM\_SITE](#ATOM_SITE) category. The DIFFRN definitions refer
to the diffraction measurements and the raw reflection data.

### <a name="_reflns.apply_dispersion_to_Fcalc"></a>\_reflns.apply\_dispersion\_to\_Fcalc

Yes or No flag on whether the anomalous dispersion scattering
components will be applied in the F complex calculation.
See [\_refln.F\_complex](#_refln.F_complex)

Values:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>yes</td><td>apply dispersion</td></tr>
  <tr><td>y</td><td>abbreviation for &quot;yes&quot;</td></tr>
  <tr><td>no</td><td>do not apply dispersion</td></tr>
  <tr><td>n</td><td>abbreviation for &quot;no&quot;</td></tr>
</table>
### <a name="_reflns.d_resolution_high"></a>\_reflns.d\_resolution\_high

Highest resolution for the final REFLN data set.
This corresponds to the smallest interpanar d value.

Units: angstroms

### <a name="_reflns.d_resolution_low"></a>\_reflns.d\_resolution\_low

Lowest resolution for the final REFLN data set.
This corresponds to the largest interpanar d value.

Units: angstroms

### <a name="_reflns.Friedel_coverage"></a>\_reflns.Friedel\_coverage

The proportion of Friedel related reflections present in the number of
the &#39;independent reflections&#39; specified by the item [\_reflns.number\_total](#_reflns.number_total).
 
This proportion is calculated as the ratio:
 
      [N(Crystal class) - N(Laue symmetry)] / N(Laue symmetry)
 
where, working from the [DIFFRN\_REFLN](#DIFFRN_REFLN) list,
 
    N(Crystal class) is the number of reflections obtained on
        averaging under the symmetry of the crystal class
    N(Laue symmetry) is the number of reflections obtained on
        averaging under the Laue symmetry.
 
  (a) For centrosymmetric structures its value is
      necessarily equal to 0.0 as the crystal class
      is identical to the Laue symmetry.
  (b) For whole-sphere data for a crystal in the space
      group P1, [\_reflns.Friedel\_coverage](#_reflns.Friedel_coverage) is equal to 1.0,
      as no reflection h k l is equivalent to -h -k -l
      in the crystal class and all Friedel pairs
      {h k l; -h -k -l} have been measured.
  (c) For whole-sphere data in space group Pmm2, the value
      will be &lt; 1.0 because although reflections h k l and
      -h -k -l are not equivalent when h k l indices are
      non-zero, they are when l=0.
  (d) For a crystal in the group Pmm2 measurements of the
      two inequivalent octants h &gt;= 0, k &gt;=0, l lead to the
      same value as in (c), whereas measurements of the
      two equivalent octants h &gt;= 0, k, l &gt;= 0 will lead to
      a zero value for [\_reflns.Friedel\_coverage](#_reflns.Friedel_coverage).

Units: none

### <a name="_reflns.Friedel_fraction_full"></a>\_reflns.Friedel\_fraction\_full

The ratio of Friedel pairs measured to [\_diffrn\_reflns.theta\_full](#_diffrn_reflns.theta_full)
to the number theoretically possible (ignoring reflections in
centric projections and systematic absences throughout).
In contrast to [\_reflns.Friedel\_coverage](#_reflns.Friedel_coverage) this can take values in
the full range 0 to 1 for any non-centrosymmetric space group,
and so one can see at a glance how completely the Friedel pairs
have been measured. For centrosymmetric space groups the value
would be given as not-applicable &#39;.&#39;

Units: none

### <a name="_reflns.Friedel_fraction_max"></a>\_reflns.Friedel\_fraction\_max

The ratio of Friedel pairs measured to [\_diffrn\_reflns.theta\_max](#_diffrn_reflns.theta_max)
to the number theoretically possible (ignoring reflections in
centric projections and systematic absences throughout).
In contrast to [\_reflns.Friedel\_coverage](#_reflns.Friedel_coverage) this can take values in
the full range 0 to 1 for any non-centrosymmetric space group,
and so one can see at a glance how completely the Friedel pairs
have been measured. For centrosymmetric space groups the value
would be given as not-applicable &#39;.&#39;

Units: none

### <a name="_reflns.limit_h_max"></a>\_reflns.limit\_h\_max

### <a name="_reflns.limit_h_min"></a>\_reflns.limit\_h\_min

### <a name="_reflns.limit_k_max"></a>\_reflns.limit\_k\_max

### <a name="_reflns.limit_k_min"></a>\_reflns.limit\_k\_min

### <a name="_reflns.limit_l_max"></a>\_reflns.limit\_l\_max

### <a name="_reflns.limit_l_min"></a>\_reflns.limit\_l\_min

### <a name="_reflns.limit_max"></a>\_reflns.limit\_max

Maximum Miller indices of refined diffraction reflections.

Units: none

### <a name="_reflns.limit_min"></a>\_reflns.limit\_min

Minimum Miller indices of refined diffraction reflections.

Units: none

### <a name="_reflns.number_gt"></a>\_reflns.number\_gt

Count of reflections in the REFLN set (not the [DIFFRN\_REFLN](#DIFFRN_REFLN) set) which
are significantly intense (see [\_reflns.threshold\_expression](#_reflns.threshold_expression)). It may
include Friedel equivalent reflections (i.e. those which are equivalent
under the Laue symmetry but inequivalent under the crystal class),
depending to the nature of the structure and the procedures used.

### <a name="_reflns.number_total"></a>\_reflns.number\_total

Number of reflections in the REFLN set (not the [DIFFRN\_REFLN](#DIFFRN_REFLN) set). It may
include Friedel equivalent reflections (i.e. those which are equivalent
under the Laue symmetry but inequivalent under the crystal class),
depending to the nature of the structure and the procedures used.

### <a name="_reflns.special_details"></a>\_reflns.special\_details

Description of the properties of the REFLN reflection list that is not
given in other data items. Should include details about the averaging
of symmetry-equivalent reflections including Friedel pairs.

### <a name="_reflns.threshold_expression"></a>\_reflns.threshold\_expression

Description of the criterion used to classify a reflection as having a
&quot;significant intensity&quot;. This criterion is usually expressed in terms
of a u(I) or u(F) threshold. &quot;u&quot; is the standard uncertainty.

## <a name="REFLNS_CLASS"></a>REFLNS\_CLASS

The CATEGORY of data items which specify the properties of reflections
in specific classes of reflections.

### <a name="_reflns_class.code"></a>\_reflns\_class.code

Code identifying a reflection class.

### <a name="_reflns_class.d_res_high"></a>\_reflns\_class.d\_res\_high

Highest resolution for the reflections in this class.
This corresponds to the smallest interpanar d value.

Units: angstroms

### <a name="_reflns_class.d_res_low"></a>\_reflns\_class.d\_res\_low

Lowest resolution for the reflections in this class.
This corresponds to the largest interpanar d value.

Units: angstroms

### <a name="_reflns_class.description"></a>\_reflns\_class.description

Description of a reflection class.

### <a name="_reflns_class.number_gt"></a>\_reflns\_class.number\_gt

Count of reflections in this REFLN class (not the [DIFFRN\_REFLN](#DIFFRN_REFLN) set)
which are significantly intense (see [\_reflns.threshold\_expression](#_reflns.threshold_expression)). It may
include Friedel equivalent reflections (i.e. those which are equivalent
under the Laue symmetry but inequivalent under the crystal class),
depending to the nature of the structure and the procedures used.

### <a name="_reflns_class.number_total"></a>\_reflns\_class.number\_total

Count of reflections in this REFLN class (not the [DIFFRN\_REFLN](#DIFFRN_REFLN) set). It
may include Friedel equivalent reflections (those which are equivalent
under the Laue symmetry but inequivalent under the crystal class),
depending to the nature of the structure and the procedures used.

### <a name="_reflns_class.R_factor_all"></a>\_reflns\_class.R\_factor\_all

Residual factor for reflections in this class used in refinement.
 
              sum | F(meas) - F(calc) |
   R(F all) = ------------------------
                    sum | F(meas) |
 
          F(meas) = the measured structure-factor amplitudes
          F(calc) = the calculated structure-factor amplitudes
 
          and the sum is taken over the specified reflections

Units: none

### <a name="_reflns_class.R_factor_gt"></a>\_reflns\_class.R\_factor\_gt

Residual factor for the reflections in this class judged
significantly intense (i.e. greater than required by the
[\_reflns.threshold\_expression](#_reflns.threshold_expression)) and included in the refinement.
 
              sum | F(meas\_gt) - F(calc) |
   R(F gt) = --------------------------------
                    sum | F(meas\_gt) |
 
          F(meas) = the measured structure-factor amplitudes
          F(calc) = the calculated structure-factor amplitudes
 
          and the sum is taken over the specified reflections

Units: none

### <a name="_reflns_class.R_Fsqd_factor"></a>\_reflns\_class.R\_Fsqd\_factor

Residual factor R(F^2^) for reflections in this class judged
significantly intense (i.e. greater than required by the
[\_reflns.threshold\_expression](#_reflns.threshold_expression)) and included in the refinement.
 
                     sum | F(meas\_gt)^2^ - F(calc)^2^ |
       R(Fsqd gt) = ------------------------------------
                             sum F(meas\_gt)^2^
 
     F(meas\_gt)^2^ = square of the &#39;observed&#39; structure-factor
     F(calc   )^2^ = square of the calculated structure-factor
 
          and the sum is taken over the specified reflections

Units: none

### <a name="_reflns_class.R_I_factor"></a>\_reflns\_class.R\_I\_factor

Residual factor R(I) for reflections in this class judged
significantly intense (i.e. greater than required by the
[\_reflns.threshold\_expression](#_reflns.threshold_expression)) and included in the refinement.
 
                  sum | I(meas\_gt) - I(calc) |
       R(I gt) =  ----------------------------
                         sum | I(meas\_gt) |
 
          I(meas\_gt) = the net &#39;observed&#39; intensity
          I(calc   ) = the net calculated intensity
 
          and the sum is taken over the specified reflections

Units: none

### <a name="_reflns_class.wR_factor_all"></a>\_reflns\_class.wR\_factor\_all

For each reflection class, the weighted residual factors for all
reflections included in the refinement. The reflections also
satisfy the resolution limits established by
[\_reflns\_class.d\_res\_high](#_reflns_class.d_res_high) and [\_reflns\_class.d\_res\_low](#_reflns_class.d_res_low).
 
     ( sum w [ Y(meas) - Y(calc) ]^2^  )^1/2^
wR = ( ------------------------------- )
     (         sum w Y(meas)^2^        )
 
    Y(meas) = the measured amplitudes specified by
              [\_refine\_ls.structure\_factor\_coef](#_refine_ls.structure_factor_coef)
    Y(calc) = the calculated amplitudes specified by
              [\_refine\_ls.structure\_factor\_coef](#_refine_ls.structure_factor_coef)
    w       = the least-squares weights
 
and the sum is taken over the reflections of this class.

Units: none

## <a name="REFLNS_SCALE"></a>REFLNS\_SCALE

The CATEGORY of data items which specify the scales needed to place
measured structure factor coefficients on the same absolute scale.

### <a name="_reflns_scale.group_code"></a>\_reflns\_scale.group\_code

Code identifying a reflection scale group. These names need not
correspond to [\_diffrn\_scale\_group.code](#_diffrn_scale_group.code) names.

### <a name="_reflns_scale.meas_F"></a>\_reflns\_scale.meas\_F

Structure factor scale for this scale group.

Units: none

### <a name="_reflns_scale.meas_F_squared"></a>\_reflns\_scale.meas\_F\_squared

Structure factor squared scale for this scale group.

Units: none

### <a name="_reflns_scale.meas_intensity"></a>\_reflns\_scale.meas\_intensity

Net intensity scale for this scale group.

Units: none

## <a name="REFLNS_SHELL"></a>REFLNS\_SHELL

The CATEGORY of data items which specify the information about
reflections divided into shells bounded by d resolution limits.

### <a name="_reflns_shell.d_res_high"></a>\_reflns\_shell.d\_res\_high

Highest resolution for the reflections in this shell.
This corresponds to the smallest interpanar d value.

Units: angstroms

### <a name="_reflns_shell.d_res_limits"></a>\_reflns\_shell.d\_res\_limits

Resolution for the reflections in this shell stored as
the list of lowest and highest values. This is the
category key.

Units: angstroms

### <a name="_reflns_shell.d_res_low"></a>\_reflns\_shell.d\_res\_low

Lowest resolution for the reflections in this shell.
This corresponds to the largest interpanar d value.

Units: angstroms

### <a name="_reflns_shell.meanI_over_suI_all"></a>\_reflns\_shell.meanI\_over\_suI\_all

Ratio of the mean intensity in a shell to the mean standard uncertainty
of the intensities in the shell.

Units: none

### <a name="_reflns_shell.meanI_over_suI_gt"></a>\_reflns\_shell.meanI\_over\_suI\_gt

Ratio of the mean intensity of significantly intense reflections (see
[\_reflns.threshold\_expression](#_reflns.threshold_expression)) in this shell to the mean standard
uncertainty of the intensities in the shell.

Units: none

### <a name="_reflns_shell.number_measured_all"></a>\_reflns\_shell.number\_measured\_all

Total count of reflections measured for this resolution shell.

### <a name="_reflns_shell.number_measured_gt"></a>\_reflns\_shell.number\_measured\_gt

Number of reflections measured for this resolution shell which are
significantly intense (see [\_reflns.threshold\_expression](#_reflns.threshold_expression)).

### <a name="_reflns_shell.number_possible"></a>\_reflns\_shell.number\_possible

Count of symmetry-unique reflections possible in this reflection shell.

### <a name="_reflns_shell.number_unique_all"></a>\_reflns\_shell.number\_unique\_all

Count of symmetry-unique reflections present in this reflection shell.

### <a name="_reflns_shell.number_unique_gt"></a>\_reflns\_shell.number\_unique\_gt

Number of symmetry-unique reflections present in this reflection shell
which are significantly intense (see [\_reflns.threshold\_expression](#_reflns.threshold_expression)).

### <a name="_reflns_shell.percent_possible_all"></a>\_reflns\_shell.percent\_possible\_all

Percentage of reflections present in this shell over that possible.

Units: none

### <a name="_reflns_shell.percent_possible_gt"></a>\_reflns\_shell.percent\_possible\_gt

Percentage of reflections present in this shell which are significantly
intense (see [\_reflns.threshold\_expression](#_reflns.threshold_expression)), over that possible.

Units: none

### <a name="_reflns_shell.Rmerge_F_all"></a>\_reflns\_shell.Rmerge\_F\_all

Rmerge(F) for all reflections in a given shell.
 
                sum~i~ ( sum~j~ | F~j~ - &lt;F&gt; | )
    Rmerge(F) = --------------------------------
                    sum~i~ ( sum~j~ &lt;F&gt; )
 
    F~j~  = the amplitude of the jth observation of reflection i
    &lt;F&gt; = the mean of the amplitudes of all observations of
           reflection i
 
    sum~i~ is taken over all reflections
    sum~j~ is taken over all observations of each reflection.

Units: none

### <a name="_reflns_shell.Rmerge_F_gt"></a>\_reflns\_shell.Rmerge\_F\_gt

Rmerge(F) for reflections in a shell which are significantly intense
(see [\_reflns.threshold\_expression](#_reflns.threshold_expression)). The residual merge expression is
shown in the [\_reflns\_shell.Rmerge\_F\_all](#_reflns_shell.Rmerge_F_all) definition.

Units: none

### <a name="_reflns_shell.Rmerge_I_all"></a>\_reflns\_shell.Rmerge\_I\_all

Rmerge(I) for all reflections in a given shell.
 
                sum~i~ ( sum~j~ | I~j~ - &lt;I&gt; | )
    Rmerge(I) = --------------------------------
                    sum~i~ ( sum~j~ &lt;I&gt; )
 
    I~j~  = the intensity of the jth observation of reflection i
    &lt;I&gt; = the mean of the intensities of all observations of
           reflection i
 
    sum~i~ is taken over all reflections
    sum~j~ is taken over all observations of each reflection.

Units: none

### <a name="_reflns_shell.Rmerge_I_gt"></a>\_reflns\_shell.Rmerge\_I\_gt

Rmerge(I) for reflections in a shell which are significantly intense
(see [\_reflns.threshold\_expression](#_reflns.threshold_expression)). The residual merge expression is
shown in the [\_reflns\_shell.Rmerge\_I\_all](#_reflns_shell.Rmerge_I_all) definition.

Units: none

## <a name="EXPTL"></a>EXPTL

The CATEGORY of data items used to specify the experimental work
prior to diffraction measurements. These include crystallization
crystal measurements and absorption-correction techniques used..

### <a name="_exptl.crystals_number"></a>\_exptl.crystals\_number

Total number of crystals used in the measurement of intensities.

### <a name="_exptl.method"></a>\_exptl.method

The method used in the experiment.

### <a name="_exptl.method_details"></a>\_exptl.method\_details

A description of special aspects of the experimental method.

### <a name="_exptl.special_details"></a>\_exptl.special\_details

Details of the experiment prior to intensity measurement.
See also [\_exptl\_crystal.preparation](#_exptl_crystal.preparation)

### <a name="_exptl.transmission_factor_max"></a>\_exptl.transmission\_factor\_max

The calculated maximum value of the transmission factor for
the specimen. Its value does not include the effects of
absorption in the specimen mount. The presence of this
item does not imply that the structure factors have been
corrected for absorption. For the applied correction see
[\_exptl\_absorpt.correction\_T\_max](#_exptl_absorpt.correction_T_max).

Units: none

### <a name="_exptl.transmission_factor_min"></a>\_exptl.transmission\_factor\_min

The calculated minimum value of the transmission factor for
the specimen. Its value does not include the effects of
absorption in the specimen mount. The presence of this
item does not imply that the structure factors have been
corrected for absorption. For the applied correction see
[\_exptl\_absorpt.correction\_T\_min](#_exptl_absorpt.correction_T_min).

Units: none

## <a name="CELL"></a>CELL

The CATEGORY of data items used to describe the parameters of
the crystal unit cell and their measurement.

### <a name="_cell.atomic_mass"></a>\_cell.atomic\_mass

Atomic mass of the contents of the unit cell. This calculated
from the atom sites present in the [ATOM\_TYPE](#ATOM_TYPE) list, rather than
the [ATOM\_SITE](#ATOM_SITE) lists of atoms in the refined model.

Units: dalton

### <a name="_cell.formula_units_Z"></a>\_cell.formula\_units\_Z

The number of the formula units in the unit cell as specified
by [\_chemical\_formula.structural](#_chemical_formula.structural), [\_chemical\_formula.moiety](#_chemical_formula.moiety) or
[\_chemical\_formula.sum](#_chemical_formula.sum).

### <a name="_cell.metric_tensor"></a>\_cell.metric\_tensor

The direct space (covariant) metric tensor used to transform
vectors and coordinates from real (direct) to reciprocal space.

### <a name="_cell.orthogonal_matrix"></a>\_cell.orthogonal\_matrix

Orthogonal matrix of the crystal unit cell. Definition uses
Rollet&#39;s axial assignments with cell vectors a,b,c aligned
with orthogonal axes X,Y,Z so that c||Z and b in plane YZ.

### <a name="_cell.special_details"></a>\_cell.special\_details

Description of special aspects of the cell choice, noting
possible alternative settings.

### <a name="_cell.volume"></a>\_cell.volume

Volume of the crystal unit cell.

Units: angstrom\_cubed

### <a name="_cell.volume_su"></a>\_cell.volume\_su

Standard uncertainty of the volume of the crystal unit cell.

Units: angstrom\_cubed

### <a name="_cell.angle_alpha"></a>\_cell.angle\_alpha

### <a name="_cell.angle_alpha_su"></a>\_cell.angle\_alpha\_su

### <a name="_cell.angle_beta"></a>\_cell.angle\_beta

### <a name="_cell.angle_beta_su"></a>\_cell.angle\_beta\_su

### <a name="_cell.angle_gamma"></a>\_cell.angle\_gamma

### <a name="_cell.angle_gamma_su"></a>\_cell.angle\_gamma\_su

### <a name="_cell.length_a"></a>\_cell.length\_a

### <a name="_cell.length_a_su"></a>\_cell.length\_a\_su

### <a name="_cell.length_b"></a>\_cell.length\_b

### <a name="_cell.length_b_su"></a>\_cell.length\_b\_su

### <a name="_cell.length_c"></a>\_cell.length\_c

### <a name="_cell.length_c_su"></a>\_cell.length\_c\_su

## <a name="CELL_MEASUREMENT"></a>CELL\_MEASUREMENT

The CATEGORY of data items used to describe the angles between
the axes in the crystal unit cell.

### <a name="_cell_measurement.pressure"></a>\_cell\_measurement.pressure

The pressure at which the unit-cell parameters were measured
(not the pressure used to synthesize the sample).

Units: kilopascals

### <a name="_cell_measurement.pressure_su"></a>\_cell\_measurement.pressure\_su

The standard uncertainty of the pressure at which
the unit-cell parameters were measured.

Units: kilopascals

### <a name="_cell_measurement.radiation"></a>\_cell\_measurement.radiation

Description of the radiation used to measure the unit-cell data.

### <a name="_cell_measurement.reflns_used"></a>\_cell\_measurement.reflns\_used

Total number of reflections used to determine the unit cell.
The reflections may be specified as cell\_measurement\_refln items.

### <a name="_cell_measurement.temperature"></a>\_cell\_measurement.temperature

The temperature at which the unit-cell parameters were measured
(not the temperature of synthesis).

Units: kelvins

### <a name="_cell_measurement.temperature_su"></a>\_cell\_measurement.temperature\_su

The standard uncertainty of the temperature of at which
the unit-cell parameters were measured.

Units: kelvins

### <a name="_cell_measurement.theta_max"></a>\_cell\_measurement.theta\_max

Maximum theta scattering angle of reflections used to measure
the crystal unit cell.

Units: degrees

### <a name="_cell_measurement.theta_min"></a>\_cell\_measurement.theta\_min

Minimum theta scattering angle of reflections used to measure
the crystal unit cell.

Units: degrees

### <a name="_cell_measurement.wavelength"></a>\_cell\_measurement.wavelength

Wavelength of the radiation used to measure the unit cell.
If this is not specified, the wavelength is assumed to be the
same as that given in [\_diffrn\_radiation\_wavelength.value](#_diffrn_radiation_wavelength.value)

Units: angstroms

## <a name="CELL_MEASUREMENT_REFLN"></a>CELL\_MEASUREMENT\_REFLN

The CATEGORY of data items used to describe the reflection data
used in the measurement of the crystal unit cell.

### <a name="_cell_measurement_refln.hkl"></a>\_cell\_measurement\_refln.hkl

Miller indices of a reflection used to measure the unit cell.

### <a name="_cell_measurement_refln.index_h"></a>\_cell\_measurement\_refln.index\_h

### <a name="_cell_measurement_refln.index_k"></a>\_cell\_measurement\_refln.index\_k

### <a name="_cell_measurement_refln.index_l"></a>\_cell\_measurement\_refln.index\_l

### <a name="_cell_measurement_refln.theta"></a>\_cell\_measurement\_refln.theta

Theta angle of reflection used to measure the crystal unit cell.

Units: degrees

### <a name="_cell.convert_Uij_to_betaij"></a>\_cell.convert\_Uij\_to\_betaij

The reciprocal space matrix for converting the U(ij) matrix of
atomic displacement parameters to a dimensionless beta(IJ) matrix.
The adp factor in a structure factor expression:
 
t = exp -2pi\*\*2 ( U11    h h a\* a\* + ...... 2 U23    k l b\* c\* )
t = exp - 0.25  ( B11    h h a\* a\* + ...... 2 B23    k l b\* c\* )
  = exp -       ( beta11 h h + ............ 2 beta23 k l )
 
    The conversion of the U or B matrices to the beta matrix
 
    beta =   C U C   =    C B C /8pi\*\*2
 
    where C is conversion matrix defined here.

### <a name="_cell.convert_Uiso_to_Uij"></a>\_cell.convert\_Uiso\_to\_Uij

The reciprocal space matrix for converting the isotropic Uiso
atomic displacement parameter to the anisotropic matrix Uij.
 
                  | 1            cos(gamma\*)   cos(beta\*)  |
 U[i,j]  = Uiso \* | cos(gamma\*)  1             cos(alpha\*) |
                  | cos(beta\*)   cos(alpha\*)   1           |
 

### <a name="_cell.reciprocal_metric_tensor"></a>\_cell.reciprocal\_metric\_tensor

The reciprocal (contravariant) metric tensor used to transform
vectors and coordinates from reciprocal space to real (direct)
space.

### <a name="_cell.reciprocal_orthogonal_matrix"></a>\_cell.reciprocal\_orthogonal\_matrix

Orthogonal matrix of the reciprocal space. The matrix may be
used to transform the non-orthogonal vector h = (h,k,l) into
the orthogonal indices p = (p,q,r)
 
                M h = p

### <a name="_cell.reciprocal_angle_alpha"></a>\_cell.reciprocal\_angle\_alpha

Reciprocal of the angle between [\_cell.length\_b](#_cell.length_b) and [\_cell.length\_c](#_cell.length_c).
Ref: Buerger, M. J. (1942). X-ray Crystallography, p. 360.
     New York: John Wiley &amp; Sons Inc.

Units: degrees

### <a name="_cell.reciprocal_angle_alpha_su"></a>\_cell.reciprocal\_angle\_alpha\_su

Standard Uncertainty of the
Reciprocal of the angle between [\_cell.length\_b](#_cell.length_b) and [\_cell.length\_c](#_cell.length_c).

Units: degrees

### <a name="_cell.reciprocal_angle_beta"></a>\_cell.reciprocal\_angle\_beta

Reciprocal of the angle between [\_cell.length\_a](#_cell.length_a) and [\_cell.length\_c](#_cell.length_c).
Ref: Buerger, M. J. (1942). X-ray Crystallography, p. 360.
     New York: John Wiley &amp; Sons Inc.

Units: degrees

### <a name="_cell.reciprocal_angle_beta_su"></a>\_cell.reciprocal\_angle\_beta\_su

Standard Uncertainty of the
Reciprocal of the angle between [\_cell.length\_a](#_cell.length_a) and [\_cell.length\_c](#_cell.length_c).

Units: degrees

### <a name="_cell.reciprocal_angle_gamma"></a>\_cell.reciprocal\_angle\_gamma

Reciprocal of the angle between [\_cell.length\_a](#_cell.length_a) and [\_cell.length\_b](#_cell.length_b).
Ref: Buerger, M. J. (1942). X-ray Crystallography, p. 360.
     New York: John Wiley &amp; Sons Inc.

Units: degrees

### <a name="_cell.reciprocal_angle_gamma_su"></a>\_cell.reciprocal\_angle\_gamma\_su

Standard Uncertainty of the
Reciprocal of the angle between [\_cell.length\_a](#_cell.length_a) and [\_cell.length\_b](#_cell.length_b).

Units: degrees

### <a name="_cell.reciprocal_length_a"></a>\_cell.reciprocal\_length\_a

Reciprocal of the [\_cell.length\_a](#_cell.length_a).

Units: reciprocal\_angstroms

### <a name="_cell.reciprocal_length_a_su"></a>\_cell.reciprocal\_length\_a\_su

Standard Uncertainty of the reciprocal of the [\_cell.length\_a](#_cell.length_a).

Units: reciprocal\_angstroms

### <a name="_cell.reciprocal_length_b"></a>\_cell.reciprocal\_length\_b

Reciprocal of the [\_cell.length\_b](#_cell.length_b).

Units: reciprocal\_angstroms

### <a name="_cell.reciprocal_length_b_su"></a>\_cell.reciprocal\_length\_b\_su

Standard Uncertainty of the reciprocal of the [\_cell.length\_b](#_cell.length_b).

Units: reciprocal\_angstroms

### <a name="_cell.reciprocal_length_c"></a>\_cell.reciprocal\_length\_c

Reciprocal of the [\_cell.length\_c](#_cell.length_c).

Units: reciprocal\_angstroms

### <a name="_cell.reciprocal_length_c_su"></a>\_cell.reciprocal\_length\_c\_su

Standard Uncertainty of the reciprocal of the [\_cell.length\_c](#_cell.length_c).

Units: reciprocal\_angstroms

### <a name="_cell.reciprocal_vector_a"></a>\_cell.reciprocal\_vector\_a

Reciprocal of the [\_cell.vector\_a](#_cell.vector_a).

### <a name="_cell.reciprocal_vector_b"></a>\_cell.reciprocal\_vector\_b

Reciprocal of the [\_cell.vector\_b](#_cell.vector_b).

### <a name="_cell.reciprocal_vector_c"></a>\_cell.reciprocal\_vector\_c

Reciprocal of the [\_cell.vector\_c](#_cell.vector_c).

### <a name="_cell.vector_a"></a>\_cell.vector\_a

The cell vector along the x axis.

### <a name="_cell.vector_b"></a>\_cell.vector\_b

The cell vector along the y axis.

### <a name="_cell.vector_c"></a>\_cell.vector\_c

The cell vector along the z axis.

## <a name="CHEMICAL"></a>CHEMICAL

The CATEGORY of data items which describe the composition and
chemical properties of the compound under study. The formula data
items must be consistent with the density, unit-cell and Z values.

### <a name="_chemical.absolute_configuration"></a>\_chemical.absolute\_configuration

Necessary conditions for this assignment are given by
     Flack, H. D. &amp; Bernardinelli, G. (1999). Acta Cryst. A55,
                  908-915. ([http://www.iucr.org/paper?sh0129](http://www.iucr.org/paper?sh0129))
     Flack, H. D. &amp; Bernardinelli, G. (2000). J. Appl. Cryst.
                  33, 1143-1148. ([http://www.iucr.org/paper?ks0021](http://www.iucr.org/paper?ks0021))

Values:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>rm</td><td>&#39;reference molecule&#39; Absolute configuration established by
  the structure determination of a compound containing a
  chiral reference molecule of known absolute configuration.</td></tr>
  <tr><td>ad</td><td>&#39;anomalous dispersion&#39; Absolute configuration established by
  a-d effects in diffraction measurements on the crystal.</td></tr>
  <tr><td>rmad</td><td>&#39;rm + ad&#39; Absolute configuration established by the structure
  determination of a compound containing a chiral reference
  molecule of known absolute configuration and confirmed by
  a-d effects in diffraction measurements on the crystal.</td></tr>
  <tr><td>syn</td><td>&#39;synthetic&#39; Absolute configuration has not been established
  by anomalous-dispersion effects in diffraction measurements on
  the crystal. The enantiomer has been assigned by reference to
  an unchanging chiral centre in the synthetic procedure.</td></tr>
  <tr><td>unk</td><td>&#39;unknown&#39; No firm chemical or a-d evidence for an assignment
  is available. An arbitrary choice of enantiomer has been made.</td></tr>
  <tr><td>.</td><td>inapplicable</td></tr>
</table>
### <a name="_chemical.compound_source"></a>\_chemical.compound\_source

Description of the source of the compound under study, or of the
parent  molecule if a simple derivative is studied. This includes
the place of  discovery for minerals or the actual source of a
natural product.

### <a name="_chemical.enantioexcess_bulk"></a>\_chemical.enantioexcess\_bulk

The enantioexcess of the bulk material from which the crystals
were grown. A value of 0.0 indicates the racemate. A value of
1.0 indicates that the compound is enantiomerically pure.
Enantioexcess is defined in the IUPAC Recommendations
(Moss et al., 1996). The composition of the crystal
and bulk must be the same.
Ref: Moss G. P. et al. (1996). Basic Terminology of
     Stereochemistry. Pure Appl. Chem., 68, 2193-2222.
     [http://www.chem.qmul.ac.uk/iupac/stereo/index.html](http://www.chem.qmul.ac.uk/iupac/stereo/index.html)

Units: none

### <a name="_chemical.enantioexcess_bulk_technique"></a>\_chemical.enantioexcess\_bulk\_technique

Technique used to determine the enantioexcess of the bulk compound.

Values:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>OA</td><td>Enantioexcess determined by measurement of the specific rotation
 of the optical activity of the bulk compound in solution.</td></tr>
  <tr><td>CD</td><td>Enantioexcess determined by measurement of the visible/near UV
 circular dichroism spectrum of the bulk compound in solution.</td></tr>
  <tr><td>EC</td><td>Enantioexcess determined by enantioselective chromatography of
 the bulk compound in solution.</td></tr>
  <tr><td>other</td><td>Enantioexcess determined by a technique not in this list.</td></tr>
</table>
### <a name="_chemical.enantioexcess_crystal"></a>\_chemical.enantioexcess\_crystal

The enantioexcess of the crystal used for the diffraction
study. A value of 0.0 indicates the racemate. A value of
1.0 indicates that the crystal is enantiomerically pure.
Enantioexcess is defined in the IUPAC Recommendations
(Moss et al., 1996).
Ref: Moss G. P. et al. (1996). Basic Terminology of
     Stereochemistry. Pure Appl. Chem., 68, 2193-2222.
     [http://www.chem.qmul.ac.uk/iupac/stereo/index.html](http://www.chem.qmul.ac.uk/iupac/stereo/index.html)

Units: none

### <a name="_chemical.enantioexcess_crystal_technique"></a>\_chemical.enantioexcess\_crystal\_technique

Technique used to determine the enantioexcess of the crystal.

Values:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>CD</td><td>Enantioexcess determined by measurement of the visible/near UV
 circular dichroism spectrum of the crystal taken into solution.</td></tr>
  <tr><td>EC</td><td>Enantioexcess determined by enantioselective chromatography of
 the crystal taken into solution.</td></tr>
  <tr><td>other</td><td>Enantioexcess determined by a technique not in this list.</td></tr>
</table>
### <a name="_chemical.identifier_inchi"></a>\_chemical.identifier\_inchi

The IUPAC International Chemical Identifier (InChI) is a
textual identifier for chemical substances, designed to provide
a standard and human-readable way to encode molecular information
and to facilitate the search for such information in databases
and on the web.
Ref: McNaught, A. (2006). Chem. Int. (IUPAC), 28 (6), 12-14.
     [http://www.iupac.org/inchi/](http://www.iupac.org/inchi/)

Examples:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>
InChI=1/C10H8/c1-2-6-10-8-4-3-7-9(10)5-1/h1-8H&#39;
  </td><td>naphthalene
  </td></tr>
</table>
### <a name="_chemical.identifier_inchi_key"></a>\_chemical.identifier\_inchi\_key

The InChIKey is a compact hashed version of the full InChI
(IUPAC International Chemical Identifier), designed to allow
for easy web searches of chemical compounds. See
[http://www.iupac.org/inchi/](http://www.iupac.org/inchi/)

Examples:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>
InChIKey=OROGSEYTTFOCAN-DNJOTXNNBG
  </td><td>codeine
  </td></tr>
</table>
### <a name="_chemical.identifier_inchi_version"></a>\_chemical.identifier\_inchi\_version

Version number of the InChI standard to which the associated
chemical identifier string applies.

### <a name="_chemical.melting_point"></a>\_chemical.melting\_point

The temperature at which a crystalline solid changes to a liquid.

Units: kelvins

### <a name="_chemical.melting_point_gt"></a>\_chemical.melting\_point\_gt

A temperature above which the melting point lies.
[\_chemical.melting\_point](#_chemical.melting_point) should be used in preference where possible.

Units: kelvins

### <a name="_chemical.melting_point_lt"></a>\_chemical.melting\_point\_lt

A temperature below which the melting point lies.
[\_chemical.melting\_point](#_chemical.melting_point) should be used in preference where possible.

Units: kelvins

### <a name="_chemical.name_common"></a>\_chemical.name\_common

Trivial name by which the compound is commonly known.

### <a name="_chemical.name_mineral"></a>\_chemical.name\_mineral

Mineral name accepted by the International Mineralogical Association.
Use only for natural minerals.

### <a name="_chemical.name_structure_type"></a>\_chemical.name\_structure\_type

Commonly used structure-type name. Usually only applied to
minerals or inorganic compounds.

### <a name="_chemical.name_systematic"></a>\_chemical.name\_systematic

IUPAC or Chemical Abstracts full name of compound.

### <a name="_chemical.optical_rotation"></a>\_chemical.optical\_rotation

The optical rotation in solution of the compound is
specified in the following format:
 
   &#39;[\a]^TEMP^~WAVE~ = SORT (c = CONC, SOLV)&#39;
 
where: TEMP is the temperature of the measurement in degrees Celsius,
       WAVE is an indication of the wavelength of the light
            used for the measurement,
       CONC is the concentration of the solution given as the
            mass of the substance in g in 100 ml of solution,
       SORT is the signed value (preceded by a + or a - sign)
            of 100.\a/(l.c), where \a is the signed optical
            rotation in degrees measured in a cell of length l in
            dm and c is the value of CONC in g, and
       SOLV is the chemical formula of the solvent.

### <a name="_chemical.properties_biological"></a>\_chemical.properties\_biological

A description of the biological properties of the material.

### <a name="_chemical.properties_physical"></a>\_chemical.properties\_physical

A description of the physical properties of the material.

### <a name="_chemical.temperature_decomposition"></a>\_chemical.temperature\_decomposition

The temperature at which a crystalline solid decomposes.

Units: kelvins

### <a name="_chemical.temperature_decomposition_gt"></a>\_chemical.temperature\_decomposition\_gt

The temperature above which a crystalline solid decomposes.
    [\_chemical.temperature\_decomposition](#_chemical.temperature_decomposition) should be used in preference.

Units: kelvins

### <a name="_chemical.temperature_decomposition_lt"></a>\_chemical.temperature\_decomposition\_lt

The temperature below which a crystalline solid decomposes.
    [\_chemical.temperature\_decomposition](#_chemical.temperature_decomposition) should be used in preference.

Units: kelvins

### <a name="_chemical.temperature_decomposition_su"></a>\_chemical.temperature\_decomposition\_su

Standard Uncertainty of the
temperature at which a crystalline solid decomposes.

Units: kelvins

### <a name="_chemical.temperature_sublimation"></a>\_chemical.temperature\_sublimation

The temperature at which a crystalline solid sublimates.

Units: kelvins

### <a name="_chemical.temperature_sublimation_gt"></a>\_chemical.temperature\_sublimation\_gt

The temperature above which a crystalline solid sublimates.
    [\_chemical.temperature\_sublimation](#_chemical.temperature_sublimation) should be used in preference.

Units: kelvins

### <a name="_chemical.temperature_sublimation_lt"></a>\_chemical.temperature\_sublimation\_lt

The temperature below which a crystalline solid sublimates.
    [\_chemical.temperature\_sublimation](#_chemical.temperature_sublimation) should be used in preference.

Units: kelvins

### <a name="_chemical.temperature_sublimation_su"></a>\_chemical.temperature\_sublimation\_su

Standard Uncertainty of the
temperature at which a crystalline solid sublimates.

Units: kelvins

## <a name="CHEMICAL_CONN_ATOM"></a>CHEMICAL\_CONN\_ATOM

The CATEGORY of data items which describe the 2D chemical structure of
the molecular species. They allow a 2D chemical diagram to be
reconstructed for use in a publication or in a database search
for structural and substructural relationships. In particular,
the chemical\_conn\_atom data items provide information about the
chemical properties of the atoms in the structure. In cases
where crystallographic and molecular symmetry elements coincide
they must also contain symmetry-generated atoms, so as to describe
a complete chemical entity.
 

### <a name="_chemical_conn_atom.charge"></a>\_chemical\_conn\_atom.charge

The net integer charge assigned to this atom. This is the
formal charge assignment normally found in chemical diagrams.

### <a name="_chemical_conn_atom.display_x"></a>\_chemical\_conn\_atom.display\_x

Cartesian coordinate (x) of the atom site in a chemical diagram. The
coordinate origin is at the lower left corner, the x axis is horizontal.

Units: none

### <a name="_chemical_conn_atom.display_y"></a>\_chemical\_conn\_atom.display\_y

Cartesian coordinate (y) of the atom site in a chemical diagram. The
coordinate origin is at the lower left corner, the y axis is vertical.

Units: none

### <a name="_chemical_conn_atom.NCA"></a>\_chemical\_conn\_atom.NCA

Total number of connected atoms excluding terminal hydrogen atoms.

### <a name="_chemical_conn_atom.NH"></a>\_chemical\_conn\_atom.NH

Total number of hydrogen atoms attached to this atom,
regardless of whether they are included in the refinement or
the atom\_site list. This number will be the same as
[\_atom\_site.attached\_hydrogens](#_atom_site.attached_hydrogens) only if none of the hydrogen
atoms appear in the atom\_site list.

### <a name="_chemical_conn_atom.number"></a>\_chemical\_conn\_atom.number

The chemical sequence number to be associated with this atom.

### <a name="_chemical_conn_atom.type_symbol"></a>\_chemical\_conn\_atom.type\_symbol

A code identifying the atom type.

## <a name="CHEMICAL_CONN_BOND"></a>CHEMICAL\_CONN\_BOND

The CATEGORY of data items which specify the connections between
the atoms sites in the chemical\_conn\_atom list and the nature
of the chemical bond between these atoms. These are details about
the two-dimensional (2D) chemical structure of the molecular species.
They allow a 2D chemical diagram to be reconstructed for use in a
publication or in a database search for structural and substructural
relationships.
 

### <a name="_chemical_conn_bond.atom_1"></a>\_chemical\_conn\_bond.atom\_1

Index id of first atom in a bond connecting two atom sites.

### <a name="_chemical_conn_bond.atom_2"></a>\_chemical\_conn\_bond.atom\_2

Index id of second atom in a bond connecting two atom sites.

### <a name="_chemical_conn_bond.distance"></a>\_chemical\_conn\_bond.distance

The value that should be taken as the target for the chemical
bond associated with the specified atoms, expressed as a
distance.

Units: angstroms

### <a name="_chemical_conn_bond.id"></a>\_chemical\_conn\_bond.id

Bond identifier composed of a list of two sequence indices
specified as [\_chemical\_conn\_atom.number](#_chemical_conn_atom.number) values.

### <a name="_chemical_conn_bond.type"></a>\_chemical\_conn\_bond.type

Code for the chemical bond type.

Values:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>sing</td><td>single bond</td></tr>
  <tr><td>doub</td><td>double bond</td></tr>
  <tr><td>trip</td><td>triple bond</td></tr>
  <tr><td>quad</td><td>quadruple bond</td></tr>
  <tr><td>arom</td><td>aromatic bond</td></tr>
  <tr><td>poly</td><td>polymeric bond</td></tr>
  <tr><td>delo</td><td>delocalized double bond</td></tr>
  <tr><td>pi</td><td>pi bond</td></tr>
</table>
## <a name="CHEMICAL_FORMULA"></a>CHEMICAL\_FORMULA

The CATEGORY of data items which specify the composition and chemical
properties of the compound. The formula data items must agree
with those that specify the density, unit-cell and Z values.
 
The following rules apply to the construction of the data items
[\_chemical\_formula.analytical](#_chemical_formula.analytical), \*.structural and \*.sum. For the
data item \*.moiety the formula construction is broken up into
residues or moieties, i.e. groups of atoms that form a molecular
unit or molecular ion. The  rules given below apply within each
moiety but different requirements apply to the way that moieties
are connected (see [\_chemical\_formula.moiety](#_chemical_formula.moiety)).
 
1. Only recognized element symbols may be used.
 
2. Each element symbol is followed by a &#39;count&#39; number. A count of
   &#39;1&#39; may be omitted.
 
3. A space or parenthesis must separate each cluster of (element
   symbol + count).
 
4. Where a group of elements is enclosed in parentheses, the
   multiplier for the group must follow the closing parentheses.
   That is, all element and group multipliers are assumed to be
   printed as subscripted numbers. [An exception to this rule
   exists for \*.moiety formulae where pre- and post-multipliers
   are permitted for molecular units].
 
5. Unless the elements are ordered in a manner that corresponds to
   their chemical structure, as in [\_chemical\_formula.structural](#_chemical_formula.structural),
   the order of the elements within any group or moiety
   depends on whether or not carbon is present. If carbon is
   present, the order should be: C, then H, then the other
   elements in alphabetical order of their symbol. If carbon is
   not present, the elements are listed purely in alphabetic order
   of their symbol. This is the &#39;Hill&#39; system used by Chemical
   Abstracts. This ordering is used in [\_chemical\_formula.moiety](#_chemical_formula.moiety)
   and [\_chemical\_formula.sum](#_chemical_formula.sum).
 
      [\_chemical\_formula.iupac](#_chemical_formula.iupac)      &#39;[Mo (C O)4 (C18 H33 P)2]&#39;
      [\_chemical\_formula.moiety](#_chemical_formula.moiety)     &#39;C40 H66 Mo O4 P2&#39;
      [\_chemical\_formula.structural](#_chemical_formula.structural) &#39;((C O)4 (P (C6 H11)3)2)Mo&#39;
      [\_chemical\_formula.sum](#_chemical_formula.sum)         &#39;C40 H66 Mo O4 P2&#39;
      [\_chemical\_formula.weight](#_chemical_formula.weight)      768.81

### <a name="_chemical_formula.analytical"></a>\_chemical\_formula.analytical

Formula determined by standard chemical analysis including trace
elements. Parentheses are used only for standard uncertainties (su&#39;s).

### <a name="_chemical_formula.iupac"></a>\_chemical\_formula.iupac

Formula expressed in conformance with IUPAC rules for inorganic
and metal-organic compounds where these conflict with the rules
for any other chemical\_formula entries. Typically used for
formatting a formula in accordance with journal rules. This
should appear in the data block in addition to the most
appropriate of the other chemical\_formula data names.
Ref: IUPAC (1990). Nomenclature of Inorganic Chemistry.
     Oxford: Blackwell Scientific Publications.

### <a name="_chemical_formula.moiety"></a>\_chemical\_formula.moiety

Formula with each discrete bonded residue or ion shown as a
separate moiety. See above [CHEMICAL\_FORMULA](#CHEMICAL_FORMULA) for rules
for writing chemical formulae. In addition to the general
formulae requirements, the following rules apply:
   1. Moieties are separated by commas &#39;,&#39;.
   2. The order of elements within a moiety follows general rule
      5 in [CHEMICAL\_FORMULA](#CHEMICAL_FORMULA).
   3. Parentheses are not used within moieties but may surround
      a moiety. Parentheses may not be nested.
   4. Charges should be placed at the end of the moiety. The
      Singlege &#39;+&#39; or &#39;-&#39; may be preceded by a numerical multiplier
      and should be separated from the last (element symbol +
      count) by a space. Pre- or post-multipliers may be used for
      individual moieties.

### <a name="_chemical_formula.structural"></a>\_chemical\_formula.structural

This formula should correspond to the structure as reported, i.e.
trace elements not included in atom type and atom site lists should
not be included. See category description for the rules for writing
chemical formulae for inorganics, organometallics, metal complexes
etc., in which  bonded groups are preserved as discrete entities
within parentheses, with post-multipliers as required. The order of
the elements should give as much information as possible about the
chemical structure.  Parentheses may be used and nested as required.
This formula should correspond to the structure as actually reported,
i.e. trace elements not included in atom-type and atom-site lists
should not be included (see also [\_chemical\_formula.analytical](#_chemical_formula.analytical)).

### <a name="_chemical_formula.sum"></a>\_chemical\_formula.sum

Chemical formulae in which all discrete bonded residues and ions are
summed over the constituent elements, following the ordering given
in rule 5 of the CATEGORY description. Parentheses normally not used.

### <a name="_chemical_formula.weight"></a>\_chemical\_formula.weight

Mass corresponding to the formulae [\_chemical\_formula.structural](#_chemical_formula.structural),
\*\_iupac, \*\_moiety or \*\_sum and, together with the Z value and cell
parameters yield the density given as [\_exptl\_crystal.density\_diffrn](#_exptl_crystal.density_diffrn).

Units: dalton

### <a name="_chemical_formula.weight_meas"></a>\_chemical\_formula.weight\_meas

Formula mass measured by a non-diffraction experiment.

Units: dalton

## <a name="EXPTL_ABSORPT"></a>EXPTL\_ABSORPT

The CATEGORY of data items used to specify the experimental details
of the  absorption measurements and corrections to the diffraction
data.

### <a name="_exptl_absorpt.coefficient_mu"></a>\_exptl\_absorpt.coefficient\_mu

Absorption coefficient mu calculated from the atomic content of
the cell, the density and the radiation wavelength.

Units: reciprocal\_millimetres

### <a name="_exptl_absorpt.correction_T_max"></a>\_exptl\_absorpt.correction\_T\_max

Maximum transmission factor for the crystal and radiation applied
to the measured intensities, it includes the correction for
absorption by the specimen mount and diffractometer as well
as by the specimen itself. These values give the transmission (T)
factor by which measured intensities have been REDUCED due to
absorption. Sometimes referred to as absorption correction A or
1/A\* (see &quot;Crystal Structure Analysis for Chemists and Biologists&quot;
by J.P. Glusker et al., Wiley)

Units: none

### <a name="_exptl_absorpt.correction_T_min"></a>\_exptl\_absorpt.correction\_T\_min

Maximum transmission factor for the crystal and radiation applied
to the measured intensities, it includes the correction for
absorption by the specimen mount and diffractometer as well
as by the specimen itself. These values give the transmission (T)
factor by which measured intensities have been REDUCED due to
absorption. Sometimes referred to as absorption correction A ori
1/A\* (see &quot;Crystal Structure Analysis for Chemists and Biologists&quot;
by J.P. Glusker et al., Wiley)

Units: none

### <a name="_exptl_absorpt.correction_type"></a>\_exptl\_absorpt.correction\_type

Code identifying the absorption correction type and method.
The &#39;empirical&#39; approach should NOT be used if more detailed
information on the crystal shape  is available.

Values:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>analytical</td><td>analytical from crystal shape</td></tr>
  <tr><td>cylinder</td><td>cylindrical</td></tr>
  <tr><td>empirical</td><td>empirical from intensities</td></tr>
  <tr><td>gaussian</td><td>Gaussian from crystal shape</td></tr>
  <tr><td>integration</td><td>integration from crystal shape</td></tr>
  <tr><td>multi-scan</td><td>symmetry-related measurements</td></tr>
  <tr><td>none</td><td>no absorption correction applied</td></tr>
  <tr><td>numerical</td><td>numerical from crystal shape</td></tr>
  <tr><td>psi-scan</td><td>psi-scan corrections</td></tr>
  <tr><td>refdelf</td><td>refined from delta-F</td></tr>
  <tr><td>sphere</td><td>spherical</td></tr>
</table>
### <a name="_exptl_absorpt.process_details"></a>\_exptl\_absorpt.process\_details

Description of the absorption correction process applied to the
measured intensities. A literature reference should be supplied
for psi-scan or multi-scan techniques.

## <a name="EXPTL_CRYSTAL"></a>EXPTL\_CRYSTAL

The CATEGORY of data items used to specify information about
crystals used in the diffraction measurements.

### <a name="_exptl_crystal.colour"></a>\_exptl\_crystal.colour

Colour description of a crystal as a list of the allowed
exptl\_crystal\_appearance states for general, intensity and hue.

### <a name="_exptl_crystal.density_diffrn"></a>\_exptl\_crystal.density\_diffrn

Crystal density calculated from crystal unit cell and atomic content.

Units: megagrams\_per\_metre\_cubed

### <a name="_exptl_crystal.density_meas"></a>\_exptl\_crystal.density\_meas

Crystal density measured using standard chemical and physical methods.

Units: megagrams\_per\_metre\_cubed

### <a name="_exptl_crystal.density_meas_gt"></a>\_exptl\_crystal.density\_meas\_gt

The value above which the density measured using standard
chemical and physical methods lies. This item is used only
when [\_exptl\_crystal.density\_meas](#_exptl_crystal.density_meas) cannot be employed. It is
intended for use in reporting information in databases and
archives which would be misleading if reported otherwise.

Units: megagrams\_per\_metre\_cubed

### <a name="_exptl_crystal.density_meas_lt"></a>\_exptl\_crystal.density\_meas\_lt

The value below which the density measured using standard
chemical and physical methods lies. This item is used only
when [\_exptl\_crystal.density\_meas](#_exptl_crystal.density_meas) cannot be employed. It is
intended for use in reporting information in databases and
archives which would be misleading if reported otherwise.

Units: megagrams\_per\_metre\_cubed

### <a name="_exptl_crystal.density_meas_su"></a>\_exptl\_crystal.density\_meas\_su

Standard Uncertainty of the
Crystal density measured using standard chemical and physical methods.

Units: megagrams\_per\_metre\_cubed

### <a name="_exptl_crystal.density_meas_temp"></a>\_exptl\_crystal.density\_meas\_temp

Temperature at which [\_exptl\_crystal.density\_meas](#_exptl_crystal.density_meas) was determined.

Units: kelvins

### <a name="_exptl_crystal.density_meas_temp_gt"></a>\_exptl\_crystal.density\_meas\_temp\_gt

Temperature above which the measured density was determined.
This item is used only when [\_exptl\_crystal.density\_meas\_temp](#_exptl_crystal.density_meas_temp)
cannot be employed. It is intended for use in reporting values
from databases which would be misleading if reported otherwise.

Units: kelvins

### <a name="_exptl_crystal.density_meas_temp_lt"></a>\_exptl\_crystal.density\_meas\_temp\_lt

Temperature below which the measured density was determined.
This item is used only when [\_exptl\_crystal.density\_meas\_temp](#_exptl_crystal.density_meas_temp)
cannot be employed. It is intended for use in reporting values
from databases which would be misleading if reported otherwise.

Units: kelvins

### <a name="_exptl_crystal.density_meas_temp_su"></a>\_exptl\_crystal.density\_meas\_temp\_su

Standard Uncertainty of the
Temperature at which [\_exptl\_crystal.density\_meas](#_exptl_crystal.density_meas) was determined.

Units: kelvins

### <a name="_exptl_crystal.density_method"></a>\_exptl\_crystal.density\_method

Description of method used to measure [\_exptl\_crystal.density\_meas](#_exptl_crystal.density_meas).

### <a name="_exptl_crystal.description"></a>\_exptl\_crystal.description

Description of the quality and habit of the crystal. The crystal
dimensions should be provided using the exptl\_crystal.size\_\* datanames.

### <a name="_exptl_crystal.F_000"></a>\_exptl\_crystal.F\_000

Number of electrons in the crystal unit cell contributing to F(000).
It may contain dispersion contributions, and is calculated as
 
     F(000) = [ (sum f~r~)^2^ + (sum f~i~)^2^ ]^1/2^
 
     f~r~   = real part of the scattering factors at theta = 0
     f~i~   = imaginary part of the scattering factors at theta = 0
 
             the sum is taken over each atom in the unit cell
 
For X-rays, non-dispersive F(000) is a positive number and counts
the effective number of electrons in the unit cell; for neutrons,
non-dispersive F(000) (which may be negative) counts the total
nuclear scattering power in the unit cell. See
   [http://reference.iucr.org/dictionary/F](http://reference.iucr.org/dictionary/F)(000)

### <a name="_exptl_crystal.id"></a>\_exptl\_crystal.id

Code identifying a crystal.

### <a name="_exptl_crystal.preparation"></a>\_exptl\_crystal.preparation

Details of crystal growth and preparation of the crystals
(e.g.  mounting) prior to the intensity measurements.

### <a name="_exptl_crystal.pressure_history"></a>\_exptl\_crystal.pressure\_history

Details concerning the pressure history of the crystals.

### <a name="_exptl_crystal.recrystallization_method"></a>\_exptl\_crystal.recrystallization\_method

Method used to recrystallize the sample. Sufficient details should
be given for the procedure to be repeated. Temperatures, solvents,
flux or carrier gases with concentrations or pressures and ambient
atmosphere details should be given.

### <a name="_exptl_crystal.size_length"></a>\_exptl\_crystal.size\_length

The length of needle/cylindrical crystals.

Units: millimetres

### <a name="_exptl_crystal.size_max"></a>\_exptl\_crystal.size\_max

The maximum dimension of a crystal.

Units: millimetres

### <a name="_exptl_crystal.size_mid"></a>\_exptl\_crystal.size\_mid

The median dimension of a crystal.

Units: millimetres

### <a name="_exptl_crystal.size_min"></a>\_exptl\_crystal.size\_min

The minimum dimension of a crystal.

Units: millimetres

### <a name="_exptl_crystal.size_rad"></a>\_exptl\_crystal.size\_rad

The radius of a spherical or cylindrical crystal.

Units: millimetres

### <a name="_exptl_crystal.thermal_history"></a>\_exptl\_crystal.thermal\_history

Details concerning the thermal history of the crystals.

## <a name="EXPTL_CRYSTAL_APPEARANCE"></a>EXPTL\_CRYSTAL\_APPEARANCE

The CATEGORY of ENUMERATION items used to specify information about the
crystal colour and appearance.

### <a name="_exptl_crystal_appearance.general"></a>\_exptl\_crystal\_appearance.general

Appearance of the crystal as prescribed state codes. Note that &#39;dull&#39;
and &#39;clear&#39; should no longer be used.

Values:

* metallic
* lustrous
* transparent
* translucent
* opaque
* dull
* clear
* .

### <a name="_exptl_crystal_appearance.hue"></a>\_exptl\_crystal\_appearance.hue

Colour hue of the crystals as prescribed state codes.

### <a name="_exptl_crystal_appearance.intensity"></a>\_exptl\_crystal\_appearance.intensity

Colour intensity of the crystal as prescribed state codes.

Values:

* dark
* light
* intense
* pale
* whitish
* blackish
* greyish
* grayish
* brownish
* reddish
* pinkish
* orangish
* yellowish
* greenish
* bluish
* .

## <a name="EXPTL_CRYSTAL_FACE"></a>EXPTL\_CRYSTAL\_FACE

The CATEGORY of data items which specify the dimensions of the
crystal used in the diffraction measurements.

### <a name="_exptl_crystal_face.diffr_chi"></a>\_exptl\_crystal\_face.diffr\_chi

### <a name="_exptl_crystal_face.diffr_kappa"></a>\_exptl\_crystal\_face.diffr\_kappa

### <a name="_exptl_crystal_face.diffr_phi"></a>\_exptl\_crystal\_face.diffr\_phi

### <a name="_exptl_crystal_face.diffr_psi"></a>\_exptl\_crystal\_face.diffr\_psi

### <a name="_exptl_crystal_face.hkl"></a>\_exptl\_crystal\_face.hkl

Miller indices of the crystal face.

### <a name="_exptl_crystal_face.index_h"></a>\_exptl\_crystal\_face.index\_h

### <a name="_exptl_crystal_face.index_k"></a>\_exptl\_crystal\_face.index\_k

### <a name="_exptl_crystal_face.index_l"></a>\_exptl\_crystal\_face.index\_l

### <a name="_exptl_crystal_face.perp_dist"></a>\_exptl\_crystal\_face.perp\_dist

Perpendicular distance of face to the centre of rotation of the crystal.

Units: millimetres

## <a name="SPACE_GROUP"></a>SPACE\_GROUP

The CATEGORY of data items used to specify space group
information about the crystal used in the diffraction measurements.

Space-group types are identified by their number as listed in
International Tables for Crystallography Volume A, or by their
Schoenflies symbol. Specific settings of the space groups can
be identified by their Hall symbol, by specifying their
symmetry operations or generators, or by giving the
transformation that relates the specific setting to the
reference setting based on International Tables Volume A and
stored in this dictionary.

The commonly used Hermann-Mauguin symbol determines the
space-group type uniquely but several different Hermann-Mauguin
symbols may refer to the same space-group type. A
Hermann-Mauguin symbol contains information on the choice of
the basis, but not on the choice of origin.

Ref: International Tables for Crystallography (2002). Volume A,
     Space-group symmetry, edited by Th. Hahn, 5th ed.
     Dordrecht: Kluwer Academic Publishers.

### <a name="_space_group.Bravais_type"></a>\_space\_group.Bravais\_type

The symbol denoting the lattice type (Bravais type) to which the
translational subgroup (vector lattice) of the space group
belongs. It consists of a lower-case letter indicating the
crystal system followed by an upper-case letter indicating
the lattice centring. The setting-independent symbol mS
replaces the setting-dependent symbols mB and mC, and the
setting-independent symbol oS replaces the setting-dependent
symbols oA, oB and oC.

Ref: International Tables for Crystallography (2002). Volume A,
     Space-group symmetry, edited by Th. Hahn, 5th ed., p. 15.
     Dordrecht: Kluwer Academic Publishers.

Values:

* aP
* mP
* mS
* oP
* oS
* oI
* oF
* tP
* tI
* hP
* hR
* cP
* cI
* cF

Examples:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>
aP
  </td><td>triclinic (anorthic) primitive lattice
  </td></tr>
</table>
### <a name="_space_group.centring_type"></a>\_space\_group.centring\_type

Symbol for the lattice centring. This symbol may be dependent
on the coordinate system chosen.

Values:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>P</td><td>primitive            no centring</td></tr>
  <tr><td>A</td><td>A-face centred       (0,1/2,1/2)</td></tr>
  <tr><td>B</td><td>B-face centred       (1/2,0,1/2)</td></tr>
  <tr><td>C</td><td>C-face centred       (1/2,1/2,0)</td></tr>
  <tr><td>F</td><td>all faces centred    (0,1/2,1/2), (1/2,0,1/2), (1/2,1/2,0)</td></tr>
  <tr><td>I</td><td>body centred         (1/2,1/2,1/2)</td></tr>
  <tr><td>R</td><td>rhombohedral obverse centred (2/3,1/3,1/3), (1/3,2/3,2/3)</td></tr>
  <tr><td>Rrev</td><td>rhombohedral reverse centred (1/3,2/3,1/3), (2/3,1/3,2/3)</td></tr>
  <tr><td>H</td><td>hexagonal centred    (2/3,1/3,0), (1/3,2/3,0)</td></tr>
</table>
### <a name="_space_group.crystal_system"></a>\_space\_group.crystal\_system

The name of the system of geometric crystal classes of space
groups (crystal system) to which the space group belongs.
Note that rhombohedral space groups belong to the
trigonal system.

Values:

* triclinic
* monoclinic
* orthorhombic
* tetragonal
* trigonal
* hexagonal
* cubic

### <a name="_space_group.IT_coordinate_system_code"></a>\_space\_group.IT\_coordinate\_system\_code

A qualifier taken from the enumeration list identifying which
setting in International Tables for Crystallography Volume A
(2002) (IT) is used.  See IT Table 4.3.2.1, Section 2.2.16,
Table 2.2.16.1, Section 2.2.16.1 and Fig. 2.2.6.4.  This item
is not computer-interpretable and cannot be used to define the
coordinate system.

Ref: International Tables for Crystallography (2002). Volume A,
     Space-group symmetry, edited by Th. Hahn, 5th ed.
     Dordrecht: Kluwer Academic Publishers.

Values:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>b1</td><td>monoclinic unique axis b, cell choice 1, abc</td></tr>
  <tr><td>b2</td><td>monoclinic unique axis b, cell choice 2, abc</td></tr>
  <tr><td>b3</td><td>monoclinic unique axis b, cell choice 3, abc</td></tr>
  <tr><td>-b1</td><td>monoclinic unique axis b, cell choice 1, c-ba</td></tr>
  <tr><td>-b2</td><td>monoclinic unique axis b, cell choice 2, c-ba</td></tr>
  <tr><td>-b3</td><td>monoclinic unique axis b, cell choice 3, c-ba</td></tr>
  <tr><td>c1</td><td>monoclinic unique axis c, cell choice 1, abc</td></tr>
  <tr><td>c2</td><td>monoclinic unique axis c, cell choice 2, abc</td></tr>
  <tr><td>c3</td><td>monoclinic unique axis c, cell choice 3, abc</td></tr>
  <tr><td>-c1</td><td>monoclinic unique axis c, cell choice 1, ba-c</td></tr>
  <tr><td>-c2</td><td>monoclinic unique axis c, cell choice 2, ba-c</td></tr>
  <tr><td>-c3</td><td>monoclinic unique axis c, cell choice 3, ba-c</td></tr>
  <tr><td>a1</td><td>monoclinic unique axis a, cell choice 1, abc</td></tr>
  <tr><td>a2</td><td>monoclinic unique axis a, cell choice 2, abc</td></tr>
  <tr><td>a3</td><td>monoclinic unique axis a, cell choice 3, abc</td></tr>
  <tr><td>-a1</td><td>monoclinic unique axis a, cell choice 1, -acb</td></tr>
  <tr><td>-a2</td><td>monoclinic unique axis a, cell choice 2, -acb</td></tr>
  <tr><td>-a3</td><td>monoclinic unique axis a, cell choice 3, -acb</td></tr>
  <tr><td>abc</td><td>orthorhombic</td></tr>
  <tr><td>ba-c</td><td>orthorhombic</td></tr>
  <tr><td>cab</td><td>orthorhombic</td></tr>
  <tr><td>-cba</td><td>orthorhombic</td></tr>
  <tr><td>bca</td><td>orthorhombic</td></tr>
  <tr><td>a-cb</td><td>orthorhombic</td></tr>
  <tr><td>1abc</td><td>orthorhombic origin choice 1</td></tr>
  <tr><td>1ba-c</td><td>orthorhombic origin choice 1</td></tr>
  <tr><td>1cab</td><td>orthorhombic origin choice 1</td></tr>
  <tr><td>1-cba</td><td>orthorhombic origin choice 1</td></tr>
  <tr><td>1bca</td><td>orthorhombic origin choice 1</td></tr>
  <tr><td>1a-cb</td><td>orthorhombic origin choice 1</td></tr>
  <tr><td>2abc</td><td>orthorhombic origin choice 2</td></tr>
  <tr><td>2ba-c</td><td>orthorhombic origin choice 2</td></tr>
  <tr><td>2cab</td><td>orthorhombic origin choice 2</td></tr>
  <tr><td>2-cba</td><td>orthorhombic origin choice 2</td></tr>
  <tr><td>2bca</td><td>orthorhombic origin choice 2</td></tr>
  <tr><td>2a-cb</td><td>orthorhombic origin choice 2</td></tr>
  <tr><td>1</td><td>tetragonal or cubic origin choice 1</td></tr>
  <tr><td>2</td><td>tetragonal or cubic origin choice 2</td></tr>
  <tr><td>h</td><td>trigonal using hexagonal axes</td></tr>
  <tr><td>r</td><td>trigonal using rhombohedral axes</td></tr>
</table>
### <a name="_space_group.IT_number"></a>\_space\_group.IT\_number

The number as assigned in International Tables for Crystallography
Vol A, specifying the proper affine class (i.e. the orientation
preserving affine class) of space groups (crystallographic space
group type) to which the space group belongs. This number defines
the space group type but not the coordinate system expressed.

### <a name="_space_group.Laue_class"></a>\_space\_group.Laue\_class

The Hermann-Mauguin symbol of the geometric crystal class of the
point group of the space group where a centre of inversion is
added if not already present.

Values:

* -1
* 2/m
* mmm
* 4/m
* 4/mmm
* -3
* -3m
* 6/m
* 6/mmm
* m-3
* m-3m

### <a name="_space_group.multiplicity"></a>\_space\_group.multiplicity

Number of unique symmetry elements in the space group.

### <a name="_space_group.name_H-M_alt"></a>\_space\_group.name\_H-M\_alt

[\_space\_group.name\_H-M\_alt](#_space_group.name_H-M_alt) allows for any Hermann-Mauguin symbol
to be given. The way in which this item is used is determined
by the user and in general is not intended to be interpreted by
computer. It may, for example, be used to give one of the
extended Hermann-Mauguin symbols given in Table 4.3.1 of
International Tables for Crystallography Vol. A (1995) or
a Hermann-Mauguin symbol for a conventional or unconventional
setting.
Each component of the space group name is separated by a
space or underscore. The use of space is strongly
recommended. The underscore is only retained because it
was used in earlier archived files. It should not be
used in new CIFs. Subscripts should appear without special
symbols. Bars should be given as negative signs before the
numbers to which they apply.
The commonly used Hermann-Mauguin symbol determines the space
group type uniquely but a given space group type may be
described by more than one Hermann-Mauguin symbol. The space
group type is best described using [\_space\_group.IT\_number](#_space_group.IT_number).
The Hermann-Mauguin symbol may contain information on the
choice of basis though not on the choice of origin. To
define the setting uniquely use [\_space\_group.name\_Hall](#_space_group.name_Hall) or
list the symmetry operations.

Examples:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>
P 1 21/m 1
  </td><td>space group No. 10
  </td></tr>
  <tr><td>
P 2/n 2/n 2/n (origin at -1)
  </td><td>space group No. 48 origin 2
  </td></tr>
  <tr><td>
R -3 2/m
  </td><td>space group No. 166 rhomb
  </td></tr>
</table>
### <a name="_space_group.name_H-M_ref"></a>\_space\_group.name\_H-M\_ref

The short international Hermann-Mauguin space-group symbol as
defined in Section 2.2.3 and given as the first item of each
space-group table in Part 7 of International Tables
for Crystallography Volume A (2002).

Each component of the space-group name is separated by a
space or an underscore character. The use of a space is
strongly recommended.  The underscore is only retained
because it was used in old CIFs. It should
not be used in new CIFs.

Subscripts should appear without special symbols. Bars
should be given as negative signs before the numbers to which
they apply.  The short international Hermann-Mauguin symbol
determines the space-group type uniquely. However, the
space-group type is better described using
[\_space\_group.IT\_number](#_space_group.IT_number) or [\_space\_group.name\_Schoenflies](#_space_group.name_Schoenflies). The
short international Hermann-Mauguin symbol contains no
information on the choice of basis or origin. To define the
setting uniquely use [\_space\_group.name\_Hall](#_space_group.name_Hall), or list the symmetry
operations or generators.

[\_space\_group.name\_H-M\_alt](#_space_group.name_H-M_alt) may be used to give the
Hermann-Mauguin symbol corresponding to the setting used.

In the enumeration list, each possible value is identified by
space-group number and Schoenflies symbol.

Ref: International Tables for Crystallography (2002). Volume A,
     Space-group symmetry, edited by Th. Hahn, 5th ed.
     Dordrecht: Kluwer Academic Publishers.

### <a name="_space_group.name_Hall"></a>\_space\_group.name\_Hall

Space group symbol defined by Hall. Each component of the
space group name is separated by a space or an underscore.
The use of space is strongly recommended because it specifies
the coordinate system. The underscore in the name is only
retained because it was used in earlier archived files. It
should not be used in new CIFs.
Ref: Hall, S. R. (1981). Acta Cryst. A37, 517-525
     [See also International Tables for Crystallography,
     Vol.B (1993) 1.4 Appendix B]

### <a name="_space_group.name_H-M_alt_description"></a>\_space\_group.name\_H-M\_alt\_description

A free-text description of the code appearing in
[\_space\_group.name\_H-M\_alt](#_space_group.name_H-M_alt).

### <a name="_space_group.name_H-M_full"></a>\_space\_group.name\_H-M\_full

The full international Hermann-Mauguin space-group symbol as
defined in Section 2.2.3 and given as the second item of the
second line of each of the space-group tables of Part 7 of
International Tables for Crystallography Volume A (2002).

Each component of the space-group name is separated by a
space or an underscore character. The use of a space is
strongly recommended.  The underscore is only retained
because it was used in old CIFs. It should not be used in
new CIFs.

Subscripts should appear without special symbols. Bars should
be given as negative signs before the numbers to which they
apply. The commonly used Hermann-Mauguin symbol determines the
space-group type uniquely but a given space-group type may
be described by more than one Hermann-Mauguin symbol. The
space-group type is best described using
[\_space\_group.IT\_number](#_space_group.IT_number) or [\_space\_group.name\_Schoenflies](#_space_group.name_Schoenflies). The
full international Hermann-Mauguin symbol contains information
about the choice of basis for monoclinic and orthorhombic
space groups but does not give information about the choice
of origin. To define the setting uniquely use
[\_space\_group.name\_Hall](#_space_group.name_Hall), or list the symmetry operations
or generators.

Ref: International Tables for Crystallography (2002). Volume A,
     Space-group symmetry, edited by Th. Hahn, 5th ed.
     Dordrecht: Kluwer Academic Publishers.

Examples:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>
P 21/n 21/m 21/a
  </td><td>full symbol for Pnma
  </td></tr>
</table>
### <a name="_space_group.name_Schoenflies"></a>\_space\_group.name\_Schoenflies

The Schoenflies symbol as listed in International Tables for
Crystallography Volume A denoting the proper affine class (i.e.
orientation-preserving affine class) of space groups
(space-group type) to which the space group belongs. This
symbol defines the space-group type independently of the
coordinate system in which the space group is expressed.

The symbol is given with a period, &#39;.&#39;, separating the
Schoenflies point group and the superscript.

Ref: International Tables for Crystallography (2002). Volume A,
     Space-group symmetry, edited by Th. Hahn, 5th ed.
     Dordrecht: Kluwer Academic Publishers.

Examples:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>
C2h.5
  </td><td>Schoenflies symbol for space group No. 14
  </td></tr>
</table>
### <a name="_space_group.Patterson_name_H-M"></a>\_space\_group.Patterson\_name\_H-M

The Hermann-Mauguin symbol of the type of that centrosymmetric
symmorphic space group to which the Patterson function belongs;
see Table 2.2.5.1 in International Tables for Crystallography
Volume A (2002).

A space separates each symbol referring to different axes.
Underscores may replace the spaces, but this use is discouraged.
Subscripts should appear without special symbols.
Bars should be given as negative signs before the number
to which they apply.

Ref: International Tables for Crystallography (2002). Volume A,
     Space-group symmetry, edited by Th. Hahn, 5th ed.,
     Table 2.2.5.1. Dordrecht: Kluwer Academic Publishers.

### <a name="_space_group.point_group_H-M"></a>\_space\_group.point\_group\_H-M

The Hermann-Mauguin symbol denoting the geometric crystal
class of space groups to which the space group belongs, and
the geometric crystal class of point groups to which the
point group of the space group belongs.

## <a name="SPACE_GROUP_GENERATOR"></a>SPACE\_GROUP\_GENERATOR

The CATEGORY of data items used to list generators for
the space group

### <a name="_space_group_generator.key"></a>\_space\_group\_generator.key

Arbitrary identifier for each entry in the [\_space\_group\_generator.xyz](#_space_group_generator.xyz)
list.

### <a name="_space_group_generator.xyz"></a>\_space\_group\_generator.xyz

A parsable string giving one of the symmetry generators of the
space group in algebraic form.  If W is a matrix representation
of the rotational part of the generator defined by the positions
and signs of x, y and z, and w is a column of translations
defined by the fractions, an equivalent position X&#39; is
generated from a given position X by

          X&#39; = WX + w.

(Note: X is used to represent the bold italic x in International
Tables for Crystallography Volume A, Section 5.)

When a list of symmetry generators is given, it is assumed
that the complete list of symmetry operations of the space
group (including the identity operation) can be generated
through repeated multiplication of the generators, that is,
(W3, w3) is an operation of the space group if (W2,w2) and
(W1,w1) [where (W1,w1) is applied first] are either operations
or generators and:

        W3 = W2 x W1
        w3 = W2 x w1 + w2.

Ref: International Tables for Crystallography (2002). Volume A,
     Space-group symmetry, edited by Th. Hahn, 5th ed.
     Dordrecht: Kluwer Academic Publishers.

Examples:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>
x,1/2-y,1/2+z
  </td><td>c glide reflection through the plane (x,1/4,z)
         chosen as one of the generators of the space group
  </td></tr>
</table>
## <a name="SPACE_GROUP_SYMOP"></a>SPACE\_GROUP\_SYMOP

The CATEGORY of data items used to describe symmetry equivalent sites
in the crystal unit cell.

### <a name="_space_group_symop.id"></a>\_space\_group\_symop.id

Index identifying each entry in the [\_space\_group\_symop.operation\_xyz](#_space_group_symop.operation_xyz)
list. It is normally the sequence number of the entry in that
list, and should be identified with the code &#39;n&#39; in the geometry
symmetry codes of the form &#39;n\_pqr&#39;. The identity operation
(i.e. [\_space\_group\_symop.operation\_xyz](#_space_group_symop.operation_xyz) set to &#39;x,y,z&#39;) should be
set to 1.

### <a name="_space_group_symop.operation_xyz"></a>\_space\_group\_symop.operation\_xyz

A parsable string giving one of the symmetry operations of the
space group in algebraic form.  If W is a matrix representation
of the rotational part of the symmetry operation defined by the
positions and signs of x, y and z, and w is a column of
translations defined by fractions, an equivalent position
X&#39; is generated from a given position X by the equation
 
          X&#39; = WX + w
 
(Note: X is used to represent bold\_italics\_x in International
Tables for Crystallography Vol. A, Part 5)
 
When a list of symmetry operations is given, it must contain
a complete set of coordinate representatives which generates
all the operations of the space group by the addition of
all primitive translations of the space group. Such
representatives are to be found as the coordinates of
the general-equivalent position in International Tables for
Crystallography Vol. A (2002), to which it is necessary to
add any centring translations shown above the
general-equivalent position.
 
That is to say, it is necessary to list explicitly all the
symmetry operations required to generate all the atoms in
the unit cell defined by the setting used.

Examples:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>
x,1/2-y,1/2+z
  </td><td>glide reflection through the plane (x,1/4,z) with glide vector (1/2)c
  </td></tr>
</table>
### <a name="_space_group_symop.operation_description"></a>\_space\_group\_symop.operation\_description

An optional text description of a particular symmetry operation
of the space group.

### <a name="_space_group_symop.R"></a>\_space\_group\_symop.R

A matrix containing the symmetry rotation operations of a space group
 
               |  r11  r12  r13  |
         R  =  |  r21  r22  r23  |
               |  r31  r32  r33  |

### <a name="_space_group_symop.RT"></a>\_space\_group\_symop.RT

The TRANSPOSE of the symmetry rotation matrix representing the point
group opertions of the space group
 
                |  r11  r21  r31  |
         RT  =  |  r12  r22  r32  |
                |  r13  r23  r33  |

### <a name="_space_group_symop.Seitz_matrix"></a>\_space\_group\_symop.Seitz\_matrix

A matrix containing the symmetry operations of a space group
in 4x4 Seitz format.
 
               |  r11  r12  r13  t1  |
  | R  T |     |  r21  r22  r23  t2  |
  | 0  1 |     |  r31  r32  r33  t3  |
               |   0    0    0    1  |

### <a name="_space_group_symop.T"></a>\_space\_group\_symop.T

A vector containing the symmetry translation operations of a space group.

## <a name="SPACE_GROUP_WYCKOFF"></a>SPACE\_GROUP\_WYCKOFF

Contains information about Wyckoff positions of a space group.
Only one site can be given for each special position but the
remainder can be generated by applying the symmetry operations
stored in [\_space\_group\_symop.operation\_xyz](#_space_group_symop.operation_xyz).

### <a name="_space_group_Wyckoff.coords_xyz"></a>\_space\_group\_Wyckoff.coords\_xyz

Coordinates of one site of a Wyckoff position expressed in
terms of its fractional coordinates (x,y,z) in the unit cell.
To generate the coordinates of all sites of this Wyckoff
position, it is necessary to multiply these coordinates by the
symmetry operations stored in [\_space\_group\_symop.operation\_xyz](#_space_group_symop.operation_xyz).

Examples:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>
x,1/2,0
  </td><td>coordinates of Wyckoff site with 2.. symmetry
  </td></tr>
</table>
### <a name="_space_group_Wyckoff.id"></a>\_space\_group\_Wyckoff.id

An arbitrary code that is unique to a particular Wyckoff position.

### <a name="_space_group_Wyckoff.letter"></a>\_space\_group\_Wyckoff.letter

The Wyckoff letter associated with this position, as given in
International Tables for Crystallography Volume A. The
enumeration value &#39;\a&#39; corresponds to the Greek letter &#39;alpha&#39;
used in International Tables.

Ref: International Tables for Crystallography (2002). Volume A,
     Space-group symmetry, edited by Th. Hahn, 5th ed.
     Dordrecht: Kluwer Academic Publishers.

Values:

* a
* b
* c
* d
* e
* f
* g
* h
* i
* j
* k
* l
* m
* n
* o
* p
* q
* r
* s
* t
* u
* v
* w
* x
* y
* z
* \a

### <a name="_space_group_Wyckoff.multiplicity"></a>\_space\_group\_Wyckoff.multiplicity

The multiplicity of this Wyckoff position as given in
International Tables Volume A.  It is the number of equivalent
sites per conventional unit cell.

Ref: International Tables for Crystallography (2002). Volume A,
     Space-group symmetry, edited by Th. Hahn, 5th ed.
     Dordrecht: Kluwer Academic Publishers.

### <a name="_space_group_Wyckoff.site_symmetry"></a>\_space\_group\_Wyckoff.site\_symmetry

The subgroup of the space group that leaves the point fixed.
It is isomorphic to a subgroup of the point group of the
space group. The site-symmetry symbol indicates the symmetry
in the symmetry direction determined by the Hermann-Mauguin
symbol of the space group (see International Tables for
Crystallography Volume A, Section 2.2.12).

Ref: International Tables for Crystallography (2002). Volume A,
     Space-group symmetry, edited by Th. Hahn, 5th ed.
     Dordrecht: Kluwer Academic Publishers.

Examples:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>
2.22
  </td><td>position 2b in space group No. 94, P 42 21 2
  </td></tr>
  <tr><td>
42.2
  </td><td>position 6b in space group No. 222, P n -3 n
  </td></tr>
  <tr><td>
2..
  </td><td>Site symmetry for the Wyckoff position 96f in space group No.
 228, F d -3 c.  The site-symmetry group is isomorphic to the
 point group 2 with the twofold axis along one of the {100}
 directions.
  </td></tr>
</table>
### <a name="_symmetry.cell_setting"></a>\_symmetry.cell\_setting

This dataname should not be used and is DEPRECATED as it is
ambiguous. 

The original definition is as follows:

The cell settings for this space-group symmetry.

Values:

* triclinic
* monoclinic
* orthorhombic
* tetragonal
* rhombohedral
* trigonal
* hexagonal
* cubic

## <a name="FUNCTION"></a>FUNCTION

The crystallographic functions the invoked in the definition
methods of CORE STRUCTURE data items defined and used with in
the Crystallographic Information Framework (CIF).

### <a name="_function.AtomType"></a>\_function.AtomType

The function
              r  =  AtomType( s )
 
returns an atom type symbol (element name) from the atom site label.

### <a name="_function.Closest"></a>\_function.Closest

The function
              d  =  Closest( v, w )
 
returns the cell translation vector required to obtain the
closest cell-translated occurence of the vector V to the vector
W.

### <a name="_function.SeitzFromJones"></a>\_function.SeitzFromJones

The function
              s  =  SeitzFromJones( j )
 
returns a 4x4 Seitz matrix from the Jones faithful representation of
the equivalent position which is a character string e.g. 1/2+x,-x,z.

### <a name="_function.SymEquiv"></a>\_function.SymEquiv

The function
                xyz&#39; =  SymEquiv( symop, xyz )
 
returns a fractional coordinate vector xyz&#39; which is input vector
xyz transformed by the input symop &#39;n\_pqr&#39; applied to the symmetry
equivalent matrix extracted from the category space\_group\_symop.

### <a name="_function.SymKey"></a>\_function.SymKey

The function
              m  =  SymKey( s )
 
returns an integer index to the Seitz matrices from the character
string of the form &#39;n\_pqr&#39;.

### <a name="_function.SymLat"></a>\_function.SymLat

The function
              v  =  SymLat( s )
 
returns a vector of the cell translations applied to the coordinates
from the character string of the form &#39;n\_pqr&#39;. i.e. p-5, q-5, r-5.

### <a name="_function.Symop"></a>\_function.Symop

The function
              s  =  Symop( n, t )
 
returns a character string of the form &#39;n\_pqr&#39; where n is the
symmetry equivalent site number and [p,q,r] is the cell translation
vector PLUS [5,5,5].

## <a name="MODEL"></a>MODEL

Items in the MODEL Category specify data for the crystal structure
postulated and modelled from the atomic coordinates derived and
refined from the diffraction information. The structural model is
described principally in terms of the geometry of the &#39;connected&#39;
atom sites and the crystal symmetry in which they reside.

## <a name="GEOM"></a>GEOM

The CATEGORY of data items used to specify the geometry
of the structural model as derived from the atomic sites.
The geometry is expressed in terms of the interatomic
angles ([GEOM\_ANGLE](#GEOM_ANGLE) data), covalent bond distances
([GEOM\_BOND](#GEOM_BOND) data), contact distances ([GEOM\_CONTACT](#GEOM_CONTACT) data),
hydrogen bonds ([GEOM\_HBOND](#GEOM_HBOND) data) and torsion geometry
([GEOM\_TORSION](#GEOM_TORSION) data).
Geometry data are usually redundant, in that they can be
calculated from other more fundamental quantities in the data
block. However, they serve the dual purposes of providing a
check on the correctness of both sets of data and of enabling
the most important geometric data to be identified for
publication by setting the appropriate publication flag.

### <a name="_geom.bond_distance_incr"></a>\_geom.bond\_distance\_incr

Increment added to the bond radii for the atomic species to
specify the maximum permitted &quot;bonded&quot; distance between two
atom sites.

Units: angstroms

### <a name="_geom.bond_distance_min"></a>\_geom.bond\_distance\_min

Minimum permitted &quot;bonded&quot; distance between two atom sites.

Units: angstroms

### <a name="_geom.contact_distance_incr"></a>\_geom.contact\_distance\_incr

Increment added to the bond radii for the atomic species to
specify the maximum permitted &quot;contact&quot; distance between two
&quot;non-bonded&quot; atom sites.

Units: angstroms

### <a name="_geom.contact_distance_min"></a>\_geom.contact\_distance\_min

Minimum permitted &quot;contact&quot; distance between two &quot;non-bonded&quot; atom sites.

Units: angstroms

### <a name="_geom.special_details"></a>\_geom.special\_details

Description of geometry information not covered by the existing data
names in the geometry categories, such as least-squares planes.

## <a name="GEOM_ANGLE"></a>GEOM\_ANGLE

The CATEGORY of data items used to specify the geometry angles in the
structural model as derived from the atomic sites.

### <a name="_geom_angle.atom_site_label_1"></a>\_geom\_angle.atom\_site\_label\_1

### <a name="_geom_angle.atom_site_label_2"></a>\_geom\_angle.atom\_site\_label\_2

The unique identifier for the vertex atom of the angle.

### <a name="_geom_angle.atom_site_label_3"></a>\_geom\_angle.atom\_site\_label\_3

### <a name="_geom_angle.distances"></a>\_geom\_angle.distances

The pair of distances between sites 1 - 2 and 2 - 3.

Units: angstroms

### <a name="_geom_angle.id"></a>\_geom\_angle.id

Atom site labels and symmetry operators as pairs for each of the
three atom sites which identify the angle. The second label-symop
pair in the list identifies the site at the apex of the angle.

### <a name="_geom_angle.publ_flag"></a>\_geom\_angle.publ\_flag

Code signals if the angle is referred to in a publication or
should be placed in a table of significant angles.

Values:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>no</td><td>do not include angle in special list</td></tr>
  <tr><td>n</td><td>abbreviation for &quot;no&quot;</td></tr>
  <tr><td>yes</td><td>do include angle in special list</td></tr>
  <tr><td>y</td><td>abbreviation for &quot;yes&quot;</td></tr>
</table>
Default value: 'no'

### <a name="_geom_angle.site_symmetry_1"></a>\_geom\_angle.site\_symmetry\_1

### <a name="_geom_angle.site_symmetry_2"></a>\_geom\_angle.site\_symmetry\_2

### <a name="_geom_angle.site_symmetry_3"></a>\_geom\_angle.site\_symmetry\_3

### <a name="_geom_angle.value"></a>\_geom\_angle.value

Angle defined by the atoms located at atom\_site\_x/site\_symmetry\_x for
x = 1,2,3. The vertex atom is at site x = 2.

Units: degrees

### <a name="_geom_angle.value_su"></a>\_geom\_angle.value\_su

Standard Uncertainty of the
angle defined by the sites identified by [\_geom\_angle.id](#_geom_angle.id)

Units: degrees

## <a name="GEOM_BOND"></a>GEOM\_BOND

The CATEGORY of data items used to specify the geometry bonds in the
structural model as derived from the atomic sites.

### <a name="_geom_bond.atom_site_label_1"></a>\_geom\_bond.atom\_site\_label\_1

### <a name="_geom_bond.atom_site_label_2"></a>\_geom\_bond.atom\_site\_label\_2

### <a name="_geom_bond.distance"></a>\_geom\_bond.distance

Intramolecular bond distance between the sites identified
by [\_geom\_bond.id](#_geom_bond.id)

Units: angstroms

### <a name="_geom_bond.distance_su"></a>\_geom\_bond.distance\_su

Standard Uncertainty of the intramolecular bond distance
between the sites identified by [\_geom\_bond.id](#_geom_bond.id)

Units: angstroms

### <a name="_geom_bond.id"></a>\_geom\_bond.id

Identity of bond distance in terms of the atom site labels and
symmetry operators as pairs for each of the two &quot;bonded&quot; atom sites.

### <a name="_geom_bond.multiplicity"></a>\_geom\_bond.multiplicity

The number of times the given bond appears in the environment
of the atoms labelled \_geom\_bond.atom\_site\_label\_1. In cases
where the full list of bonds is given, one of the series of
equivalent bonds may be assigned the appropriate multiplicity
while the others are assigned a value of 0.

### <a name="_geom_bond.publ_flag"></a>\_geom\_bond.publ\_flag

This code signals whether the angle is referred to in a
publication or should be placed in a table of significant angles.

Values:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>no</td><td>do not include bond in special list</td></tr>
  <tr><td>n</td><td>abbreviation for &quot;no&quot;</td></tr>
  <tr><td>yes</td><td>do include bond in special list</td></tr>
  <tr><td>y</td><td>abbreviation for &quot;yes&quot;</td></tr>
</table>
Default value: 'no'

### <a name="_geom_bond.site_symmetry_1"></a>\_geom\_bond.site\_symmetry\_1

### <a name="_geom_bond.site_symmetry_2"></a>\_geom\_bond.site\_symmetry\_2

### <a name="_geom_bond.valence"></a>\_geom\_bond.valence

Bond valence calculated from the bond distance.

Units: electrons

## <a name="GEOM_CONTACT"></a>GEOM\_CONTACT

The CATEGORY of data items used to specify the interatomic
contact distances in the structural model.

### <a name="_geom_contact.atom_site_label_1"></a>\_geom\_contact.atom\_site\_label\_1

### <a name="_geom_contact.atom_site_label_2"></a>\_geom\_contact.atom\_site\_label\_2

### <a name="_geom_contact.distance"></a>\_geom\_contact.distance

Intermolecular distance between the atomic sites identified
by [\_geom\_contact.id](#_geom_contact.id)

Units: angstroms

### <a name="_geom_contact.distance_su"></a>\_geom\_contact.distance\_su

Standard Uncertainty of the intermolecular distance between
the atomic sites identified by [\_geom\_contact.id](#_geom_contact.id)

Units: angstroms

### <a name="_geom_contact.id"></a>\_geom\_contact.id

Atom site labels and symmetry operators as pairs for each of the
two atom sites which define the geom\_contact bond.

### <a name="_geom_contact.publ_flag"></a>\_geom\_contact.publ\_flag

This code signals whether the contact distance is referred to
in a publication or should be placed in a list of significant
contact distances.

Values:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>no</td><td>do not include distance in special list</td></tr>
  <tr><td>n</td><td>abbreviation for &quot;no&quot;</td></tr>
  <tr><td>yes</td><td>do include distance in special list</td></tr>
  <tr><td>y</td><td>abbreviation for &quot;yes&quot;</td></tr>
</table>
Default value: 'no'

### <a name="_geom_contact.site_symmetry_1"></a>\_geom\_contact.site\_symmetry\_1

### <a name="_geom_contact.site_symmetry_2"></a>\_geom\_contact.site\_symmetry\_2

## <a name="GEOM_HBOND"></a>GEOM\_HBOND

The CATEGORY of data items used to specify the hydrogen bond
distances in the structural model as derived from atomic sites.

### <a name="_geom_hbond.angle_DHA"></a>\_geom\_hbond.angle\_DHA

Angle subtended by the sites identified by [\_geom\_hbond.id](#_geom_hbond.id).
The hydrogen at site H is at the apex of the angle.

Units: degrees

### <a name="_geom_hbond.angle_DHA_su"></a>\_geom\_hbond.angle\_DHA\_su

The standard uncertainty of the angle subtended by the sites identified
by [\_geom\_hbond.id](#_geom_hbond.id). The hydrogen at site H is at the apex of the angle.

Units: degrees

### <a name="_geom_hbond.atom_site_label_A"></a>\_geom\_hbond.atom\_site\_label\_A

### <a name="_geom_hbond.atom_site_label_D"></a>\_geom\_hbond.atom\_site\_label\_D

### <a name="_geom_hbond.atom_site_label_H"></a>\_geom\_hbond.atom\_site\_label\_H

### <a name="_geom_hbond.distance_DA"></a>\_geom\_hbond.distance\_DA

The set of data items which specify the distance between the
three atom sites identified by [\_geom\_hbond.id](#_geom_hbond.id).

Units: angstroms

### <a name="_geom_hbond.distance_DA_su"></a>\_geom\_hbond.distance\_DA\_su

Standard Uncertainty of the
set of data items which specify the distance between the
three atom sites identified by [\_geom\_hbond.id](#_geom_hbond.id).

Units: angstroms

### <a name="_geom_hbond.distance_DH"></a>\_geom\_hbond.distance\_DH

The set of data items which specify the distance between the
three atom sites identified by [\_geom\_hbond.id](#_geom_hbond.id).

Units: angstroms

### <a name="_geom_hbond.distance_DH_su"></a>\_geom\_hbond.distance\_DH\_su

Standard Uncertainty of the
set of data items which specify the distance between the
three atom sites identified by [\_geom\_hbond.id](#_geom_hbond.id).

Units: angstroms

### <a name="_geom_hbond.distance_HA"></a>\_geom\_hbond.distance\_HA

The set of data items which specify the distance between the
three atom sites identified by [\_geom\_hbond.id](#_geom_hbond.id).

Units: angstroms

### <a name="_geom_hbond.distance_HA_su"></a>\_geom\_hbond.distance\_HA\_su

Standard Uncertainty of the
set of data items which specify the distance between the
three atom sites identified by [\_geom\_hbond.id](#_geom_hbond.id).

Units: angstroms

### <a name="_geom_hbond.id"></a>\_geom\_hbond.id

Atom site labels and symmetry operators as pairs for each of the
three atom sites which define the hydrogen angle and distances.
Site H is at the apex of the angle.

### <a name="_geom_hbond.publ_flag"></a>\_geom\_hbond.publ\_flag

This code signals whether the hydrogen-bond information
is referred to in a publication or should be placed in a
table of significant hydrogen-bond geometry.

Values:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>no</td><td>do not include bond in special list</td></tr>
  <tr><td>n</td><td>abbreviation for &quot;no&quot;</td></tr>
  <tr><td>yes</td><td>do include bond in special list</td></tr>
  <tr><td>y</td><td>abbreviation for &quot;yes&quot;</td></tr>
</table>
Default value: 'no'

### <a name="_geom_hbond.site_symmetry_A"></a>\_geom\_hbond.site\_symmetry\_A

### <a name="_geom_hbond.site_symmetry_D"></a>\_geom\_hbond.site\_symmetry\_D

### <a name="_geom_hbond.site_symmetry_H"></a>\_geom\_hbond.site\_symmetry\_H

## <a name="GEOM_TORSION"></a>GEOM\_TORSION

The CATEGORY of data items used to specify the torsion angles in the
structural model as derived from the atomic sites.

### <a name="_geom_torsion.angle"></a>\_geom\_torsion.angle

Angle defined by the sites identified by [\_geom\_torsion.id](#_geom_torsion.id).
The torsion-angle definition should be that of Klyne and Prelog.
The vector direction \*\_label\_2 to \*\_label\_3 is the viewing
direction, and the torsion angle is the angle of twist required
to superimpose the projection of the vector between site 2 and
site 1 onto the projection of the vector between site 3 and
site 4. Clockwise torsions are positive, anticlockwise torsions
are negative.
Ref: Klyne, W. &amp; Prelog, V. (1960). Experientia, 16, 521-523.

Units: degrees

### <a name="_geom_torsion.angle_su"></a>\_geom\_torsion.angle\_su

Standard Uncertainty of the torsion angle.

Units: degrees

### <a name="_geom_torsion.atom_site_label_1"></a>\_geom\_torsion.atom\_site\_label\_1

### <a name="_geom_torsion.atom_site_label_2"></a>\_geom\_torsion.atom\_site\_label\_2

### <a name="_geom_torsion.atom_site_label_3"></a>\_geom\_torsion.atom\_site\_label\_3

### <a name="_geom_torsion.atom_site_label_4"></a>\_geom\_torsion.atom\_site\_label\_4

### <a name="_geom_torsion.distances"></a>\_geom\_torsion.distances

Distances between sites 1 - 2, 2 - 3 and 3 - 4.

Units: angstroms

### <a name="_geom_torsion.id"></a>\_geom\_torsion.id

Atom site labels and symmetry operators as pairs for each of the
four atom sites which define the torsion angle.

### <a name="_geom_torsion.publ_flag"></a>\_geom\_torsion.publ\_flag

Code signals if the torsion angle is required for publication.

Values:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>yes</td><td>publish</td></tr>
  <tr><td>y</td><td>abbreviation for &quot;yes&quot;</td></tr>
  <tr><td>no</td><td>do not publish</td></tr>
  <tr><td>n</td><td>abbreviation for &quot;no&quot;</td></tr>
</table>
Default value: 'no'

### <a name="_geom_torsion.site_symmetry_1"></a>\_geom\_torsion.site\_symmetry\_1

### <a name="_geom_torsion.site_symmetry_2"></a>\_geom\_torsion.site\_symmetry\_2

### <a name="_geom_torsion.site_symmetry_3"></a>\_geom\_torsion.site\_symmetry\_3

### <a name="_geom_torsion.site_symmetry_4"></a>\_geom\_torsion.site\_symmetry\_4

## <a name="MODEL_SITE"></a>MODEL\_SITE

The CATEGORY of data items used to describe atomic sites and
connections in the proposed atomic model.

### <a name="_model_site.adp_eigen_system"></a>\_model\_site.adp\_eigen\_system

The set of three adp eigenvales and associated eigenvectors
in the form of 4 element List. Each list has the form
 
              (val, vecX, vecY, vecZ)
 
where the vector elements are direction cosines to the orthogonal
axes X,Y,Z. The lists are sorted in descending magnitude of val.
That is, the list with the largest val is first, and the smallest
val is last.

### <a name="_model_site.adp_matrix_beta"></a>\_model\_site.adp\_matrix\_beta

Matrix of dimensionless anisotropic atomic displacement parameters.

### <a name="_model_site.Cartn_xyz"></a>\_model\_site.Cartn\_xyz

Vector of Cartesian (orthogonal angstrom) atom site coordinates.

### <a name="_model_site.display_colour"></a>\_model\_site.display\_colour

Display colour code assigned to this atom site. Note that the
possible colours are enumerated in the colour\_RGB list, and
the default code is enumerated in the colour\_hue list.

### <a name="_model_site.fract_xyz"></a>\_model\_site.fract\_xyz

Vector of fractional atom site coordinates.

### <a name="_model_site.id"></a>\_model\_site.id

Identifier of model site in terms of the atom site label and
symmetry operator.

### <a name="_model_site.index"></a>\_model\_site.index

Index number of an atomic site in the connected molecule.

### <a name="_model_site.label"></a>\_model\_site.label

Code identifies a site in the atom\_site category of data.

### <a name="_model_site.mole_index"></a>\_model\_site.mole\_index

Index number of a distinct molecules in the cell, not related by
symmetry.

### <a name="_model_site.radius_bond"></a>\_model\_site.radius\_bond

Atomic radius of atom located at this site.

Units: angstroms

### <a name="_model_site.radius_contact"></a>\_model\_site.radius\_contact

Atomic contact radius of atom specie located at this site.

Units: angstroms

### <a name="_model_site.symop"></a>\_model\_site.symop

### <a name="_model_site.type_symbol"></a>\_model\_site.type\_symbol

Code to identify the atom specie(s) occupying this site.

## <a name="VALENCE"></a>VALENCE

The CATEGORY of items used to specify bond valence parameters
used to calculate bond valences from bond lengths.

## <a name="VALENCE_PARAM"></a>VALENCE\_PARAM

The CATEGORY of items for listing bond valences.

### <a name="_valence_param.atom_1"></a>\_valence\_param.atom\_1

Atom type symbol for atom 1 forming a bond whose
valence parameters are given in this category.

### <a name="_valence_param.atom_1_valence"></a>\_valence\_param.atom\_1\_valence

The formal charge of the atom 1 whose bond
valence parameters are given in this category.

### <a name="_valence_param.atom_2"></a>\_valence\_param.atom\_2

Atom type symbol for atom 2 forming a bond whose
valence parameters are given in this category.

### <a name="_valence_param.atom_2_valence"></a>\_valence\_param.atom\_2\_valence

The formal charge of the atom 2 whose bond
valence parameters are given in this category.

### <a name="_valence_param.B"></a>\_valence\_param.B

The bond valence parameter B used in the expression
s = exp[(Ro - R)/B] where s is the valence of bond length R.

Units: angstroms

### <a name="_valence_param.details"></a>\_valence\_param.details

Details of valence parameters of stated bond.

### <a name="_valence_param.id"></a>\_valence\_param.id

Unique index loop number of the valence parameter loop.

### <a name="_valence_param.ref_id"></a>\_valence\_param.ref\_id

Code linking parameters to the key [\_valence\_ref.id](#_valence_ref.id) key
in the reference list in category [VALENCE\_REF](#VALENCE_REF).

### <a name="_valence_param.Ro"></a>\_valence\_param.Ro

The bond valence parameter Ro used in the expression
s = exp[(Ro - R)/B] where s is the valence of bond length R.

Units: angstroms

## <a name="VALENCE_REF"></a>VALENCE\_REF

The CATEGORY of items for listing valence references.

### <a name="_valence_ref.id"></a>\_valence\_ref.id

Unique loop code of the valence references.

### <a name="_valence_ref.reference"></a>\_valence\_ref.reference

Literature reference from which the valence parameters
identified by [\_valence\_param.id](#_valence_param.id) were taken

## <a name="PUBLICATION"></a>PUBLICATION

The DICTIONARY group encompassing the CORE PUBLICATION data items defined
and used with in the Crystallographic Information Framework (CIF).

## <a name="AUDIT"></a>AUDIT

The CATEGORY of data items used to record details about the
creation and subsequent updating of the data block.

### <a name="_audit.block_code"></a>\_audit.block\_code

A unique block code identifier for each revision.

### <a name="_audit.block_doi"></a>\_audit.block\_doi

The digital object identifier (DOI) registered to identify
 the data set publication represented by the current
 datablock. This can be used as a unique identifier for
 the datablock so long as the code used is a valid DOI
 (i.e. begins with a valid publisher prefix assigned by a
 Registration Agency and a suffix guaranteed to be unique
 by the publisher) and has had its metadata deposited
 with a DOI Registration Agency.

 A DOI is a unique character string identifying any
 object of intellectual property. It provides a
 persistent identifier for an object on a digital network
 and permits the association of related current data in a
 structured extensible way. A DOI is an implementation
 of the Internet concepts of Uniform Resource Name and
 Universal Resource Locator managed according to the
 specifications of the International DOI Foundation (see
 [http://www.doi.org](http://www.doi.org)).

### <a name="_audit.creation_date"></a>\_audit.creation\_date

The timestamp of the data revision.

### <a name="_audit.creation_method"></a>\_audit.creation\_method

A description of how the revision was applied to the data.

### <a name="_audit.schema"></a>\_audit.schema

This dataname identifies the type of information contained in the
datablock. Software written for one schema will not, in general,
correctly interpret datafiles written against a different schema.

Specifically, each value of [\_audit.schema](#_audit.schema) corresponds to a list
of categories that were (potentially implicitly) restricted to a
single packet in the default Base schema, but which can contain
multiple packets in the specified schema.  All categories
containing child keys of the listed categories may also contain
multiple packets and do not need to be listed.

The category list for each schema may instead be determined from
examination of the dictionaries that this datablock conforms to (see
[\_audit\_conform.dict\_name](#_audit_conform.dict_name)).


Values:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>Base</td><td>Original Core CIF schema</td></tr>
  <tr><td>Space group tables</td><td>space_group category is looped</td></tr>
  <tr><td>Entry</td><td>entry category is defined and looped: information from multiple datablocks in one block</td></tr>
  <tr><td>Custom</td><td>Examine dictionaries provided in _audit_conform</td></tr>
  <tr><td>Local</td><td>Locally modified dictionaries. These datafiles should not be distributed</td></tr>
</table>
Default value: 'Base'

### <a name="_audit.update_record"></a>\_audit.update\_record

A description of the revision applied to the data.

## <a name="AUDIT_AUTHOR"></a>AUDIT\_AUTHOR

The CATEGORY of data items used for author(s) details.

### <a name="_audit_author.address"></a>\_audit\_author.address

The address of an author of this data block. If there are
multiple authors, [\_audit\_author.address](#_audit_author.address) is looped with
[\_audit\_author.name](#_audit_author.name).

### <a name="_audit_author.name"></a>\_audit\_author.name

The name of an author of this data block. If there are multiple
authors, [\_audit\_author.name](#_audit_author.name) is looped with [\_audit\_author.address](#_audit_author.address).
The family name(s), followed by a comma and including any
dynastic components, precedes the first name(s) or initial(s).
 

## <a name="AUDIT_CONFORM"></a>AUDIT\_CONFORM

The CATEGORY of data items used describe dictionary versions
by which data names in the current data block are conformant.

### <a name="_audit_conform.dict_location"></a>\_audit\_conform.dict\_location

File name or uniform resource locator (URL) where the
conformant data dictionary resides.

### <a name="_audit_conform.dict_name"></a>\_audit\_conform.dict\_name

Name identifying highest-level data dictionary defining
data names used in this file.

### <a name="_audit_conform.dict_version"></a>\_audit\_conform.dict\_version

Code for the version of data dictionary defining data names
used in this file.

## <a name="AUDIT_CONTACT_AUTHOR"></a>AUDIT\_CONTACT\_AUTHOR

The CATEGORY of data items used for contact author(s) details.

### <a name="_audit_contact_author.address"></a>\_audit\_contact\_author.address

The mailing address of the author of the data block to whom
correspondence should be addressed.

### <a name="_audit_contact_author.email"></a>\_audit\_contact\_author.email

The electronic mail address of the author of the data block
to whom correspondence should be addressed, in a form
recognizable to international networks. The format of e-mail
addresses is given in Section 3.4, Address Specification, of
Internet Message Format, RFC 2822, P. Resnick (Editor),
Network Standards Group, April 2001.

### <a name="_audit_contact_author.fax"></a>\_audit\_contact\_author.fax

Facsimile telephone number of the author submitting the manuscript
and data block.
The recommended style is the international dialing prefix, followed
by the area code in parentheses, followed by the local number with
no spaces. The earlier convention of including the international
dialing prefix in parentheses is no longer recommended.

### <a name="_audit_contact_author.name"></a>\_audit\_contact\_author.name

The name of the author of the data block to whom correspondence
should be addressed. The family name(s), followed by a comma and
including any dynastic components, precedes the first name(s) or
initial(s).

### <a name="_audit_contact_author.phone"></a>\_audit\_contact\_author.phone

Telephone number of author submitting the manuscript and data block.
The recommended style is the international dialing prefix,
followed by the area code in parentheses, followed by the
local number and any extension number prefixed by &#39;x&#39;, with
no spaces. The earlier convention of including the international
dialing prefix in parentheses is no longer recommended.

## <a name="AUDIT_LINK"></a>AUDIT\_LINK

The CATEGORY of data items used to record details about the
relationships between data blocks in the current CIF.

### <a name="_audit_link.block_code"></a>\_audit\_link.block\_code

The value of [\_audit.block\_code](#_audit.block_code) associated with a data block
in the current file related to the current data block. The
special value &#39;.&#39; may be used to refer to the current data
block for completeness.

### <a name="_audit_link.block_description"></a>\_audit\_link.block\_description

Description of the relationship of the referenced data block
to the current one.

## <a name="CITATION"></a>CITATION

Data items in the CITATION category record details about the
literature cited as being relevant to the contents of the data
block.

### <a name="_citation.abstract"></a>\_citation.abstract

Abstract for the citation. This is used most when the
citation is extracted from a bibliographic database that
contains full text or abstract information.

### <a name="_citation.abstract_id_CAS"></a>\_citation.abstract\_id\_CAS

Chemical Abstracts Service (CAS) abstract identifier.

### <a name="_citation.book_id_ISBN"></a>\_citation.book\_id\_ISBN

International Standard Book Number (ISBN) for book chap. cited.

### <a name="_citation.book_publisher"></a>\_citation.book\_publisher

Publisher of the citation; relevant for book chapters.

### <a name="_citation.book_publisher_city"></a>\_citation.book\_publisher\_city

Location of publisher of the citation; relevant for book chapters.

### <a name="_citation.book_title"></a>\_citation.book\_title

Title of the book in which the citation appeared.

### <a name="_citation.coordinate_linkage"></a>\_citation.coordinate\_linkage

Code specifies whether this citation is concerned with precisely
the set of coordinates given in the data block. If, for instance,
the publication described the same structure, but the coordinates
had undergone further refinement prior to creation of the data
block, the value of this data item would be &#39;no&#39;.

Values:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>no</td><td>citation unrelated to current coordinates</td></tr>
  <tr><td>n</td><td>abbreviation for &quot;no&quot;</td></tr>
  <tr><td>yes</td><td>citation related to current coordinates</td></tr>
  <tr><td>y</td><td>abbreviation for &quot;yes&quot;</td></tr>
</table>
### <a name="_citation.country"></a>\_citation.country

Country of publication; for journal articles and book chapters.

### <a name="_citation.database_id_CSD"></a>\_citation.database\_id\_CSD

Identifier (&#39;refcode&#39;) of the database record in the Cambridge
Structural Database containing details of the cited structure.

### <a name="_citation.database_id_Medline"></a>\_citation.database\_id\_Medline

i    Medline accession number categorizing a bibliographic entry.

### <a name="_citation.doi"></a>\_citation.doi

The Digital Object Identifier (DOI) of the cited work.

 A DOI is a unique character string identifying any
 object of intellectual property. It provides a
 persistent identifier for an object on a digital network
 and permits the association of related current data in a
 structured extensible way. A DOI is an implementation
 of the Internet concepts of Uniform Resource Name and
 Universal Resource Locator managed according to the
 specifications of the International DOI Foundation (see
 [http://www.doi.org](http://www.doi.org)).

### <a name="_citation.id"></a>\_citation.id

Unique identifier to the CITATION list. A value of &#39;primary&#39;
should be used to indicate the citation that the author(s)
consider to be the most pertinent to the contents of the data
block.  Note that this item need not be a number;  it can be
any unique identifier.

### <a name="_citation.journal_abbrev"></a>\_citation.journal\_abbrev

Abbreviated name of the journal cited as given in the Chemical
Abstracts Service Source Index.

### <a name="_citation.journal_full"></a>\_citation.journal\_full

Full name of the journal cited; relevant for journal articles.

### <a name="_citation.journal_id_ASTM"></a>\_citation.journal\_id\_ASTM

American Society for the Testing of Materials (ASTM) code assigned
to the journal cited (also referred to as the CODEN designator of
the Chemical Abstracts Service); relevant for journal articles.

### <a name="_citation.journal_id_CSD"></a>\_citation.journal\_id\_CSD

The Cambridge Structural Database (CSD) code assigned to the
journal cited; relevant for journal articles. This is also the
system used at the Protein Data Bank (PDB).

### <a name="_citation.journal_id_ISSN"></a>\_citation.journal\_id\_ISSN

The International Standard Serial Number (ISSN) code assigned to
the journal cited;  relevant for journal articles.

### <a name="_citation.journal_issue"></a>\_citation.journal\_issue

Issue number of the journal cited;  relevant for articles.

### <a name="_citation.journal_volume"></a>\_citation.journal\_volume

Volume number of the journal cited;  relevant for articles.

### <a name="_citation.language"></a>\_citation.language

Language in which the citation appears.

### <a name="_citation.page_first"></a>\_citation.page\_first

First page of citation; relevant for articles and book chapters.

### <a name="_citation.page_last"></a>\_citation.page\_last

Last page of citation; relevant for articles and book chapters.

### <a name="_citation.publisher"></a>\_citation.publisher

The name of the publisher of the cited work. This
 should be used for citations of journal articles or
 datasets (in the latter case the publisher could be a
 curated database). For books or book chapters use
 [\_citation.book\_publisher](#_citation.book_publisher).

### <a name="_citation.special_details"></a>\_citation.special\_details

Special aspects of the relationship of the data block contents
to the literature item cited.

### <a name="_citation.title"></a>\_citation.title

Title of citation; relevant for articles and book chapters.

### <a name="_citation.year"></a>\_citation.year

Year of citation; relevant for articles and book chapters.

## <a name="CITATION_AUTHOR"></a>CITATION\_AUTHOR

Category of items describing citation author(s) details.

### <a name="_citation_author.key"></a>\_citation\_author.key

Value is a unique key to a set of [CITATION\_AUTHOR](#CITATION_AUTHOR) items
in a looped list.

### <a name="_citation_author.citation_id"></a>\_citation\_author.citation\_id

Code identifier in the CITATION data list. The value of must match
an identifier specified in the CITATION list.

### <a name="_citation_author.name"></a>\_citation\_author.name

Name of citation author; relevant for articles and book chapters.
The family name(s), followed by a comma and including any
dynastic components, precedes the first name(s) or initial(s).

### <a name="_citation_author.ordinal"></a>\_citation\_author.ordinal

Ordinal code specifies the order of the author&#39;s name in the list
of authors of the citation.

## <a name="CITATION_EDITOR"></a>CITATION\_EDITOR

Category of items describing citation editor(s) details.

### <a name="_citation_editor.citation_id"></a>\_citation\_editor.citation\_id

Code identifier in the CITATION list. The value must match an
identifier specified by [\_citation.id](#_citation.id) in the CITATION list.

### <a name="_citation_editor.id"></a>\_citation\_editor.id

Value is a unique key to a set of [CITATION\_EDITOR](#CITATION_EDITOR) items
in a looped list.

### <a name="_citation_editor.name"></a>\_citation\_editor.name

Name of citation editor; relevant for book chapters.
The family name(s), followed by a comma and including any
dynastic components, precedes the first name(s) or initial(s).

### <a name="_citation_editor.ordinal"></a>\_citation\_editor.ordinal

This data item defines the order of the editor&#39;s name in the
list of editors of a citation.

## <a name="COMPUTING"></a>COMPUTING

The CATEGORY of data items used to record details of the
computer programs used in the crystal structure analysis.

### <a name="_computing.cell_refinement"></a>\_computing.cell\_refinement

Brief description of software used for cell refinement.

### <a name="_computing.diffrn_collection"></a>\_computing.diffrn\_collection

Description of software used to measure diffraction data.

### <a name="_computing.diffrn_reduction"></a>\_computing.diffrn\_reduction

Description of software used to convert diffraction data
to measured structure factors.

### <a name="_computing.molecular_graphics"></a>\_computing.molecular\_graphics

Brief description of software used for molecular graphics.

### <a name="_computing.publication_material"></a>\_computing.publication\_material

Brief description of software used for publication material.

### <a name="_computing.structure_refinement"></a>\_computing.structure\_refinement

Brief description of software used for structure refinement.

### <a name="_computing.structure_solution"></a>\_computing.structure\_solution

Brief description of software used for structure solution.

## <a name="DATABASE"></a>DATABASE

The CATEGORY of data items recording database deposition.

### <a name="_database.CSD_history"></a>\_database.CSD\_history

The history of changes made by the Cambridge Crystallographic Data
Centre and incorporated into the Cambridge Structural Database (CSD).

### <a name="_database.dataset_doi"></a>\_database.dataset\_doi

The digital object identifier (DOI) registered to identify
 a data set publication associated with the structure
 described in the current datablock. This should be used
 for a dataset obtained from a curated database such as
 CSD or PDB.

 A DOI is a unique character string identifying any
 object of intellectual property. It provides a
 persistent identifier for an object on a digital network
 and permits the association of related current data in a
 structured extensible way. A DOI is an implementation
 of the Internet concepts of Uniform Resource Name and
 Universal Resource Locator managed according to the
 specifications of the International DOI Foundation (see
 [http://www.doi.org](http://www.doi.org)).

### <a name="_database.journal_ASTM"></a>\_database.journal\_ASTM

ASTM CODEN designator for a journal as given in the Chemical
Source List maintained by the Chemical Abstracts Service.

### <a name="_database.journal_CSD"></a>\_database.journal\_CSD

The journal code used in the Cambridge Structural Database.

## <a name="DATABASE_CODE"></a>DATABASE\_CODE

The CATEGORY of data items recording database deposition. These data items
are assigned by database managers and should only appear in a CIF if they
originate from that source.

### <a name="_database_code.CAS"></a>\_database\_code.CAS

Code assigned by the Chemical Abstracts Service.

### <a name="_database_code.COD"></a>\_database\_code.COD

Code assigned by Crystallography Open Database (COD).

### <a name="_database_code.CSD"></a>\_database\_code.CSD

Code assigned by the Cambridge Structural Database.

### <a name="_database_code.depnum_ccdc_archive"></a>\_database\_code.depnum\_ccdc\_archive

Deposition numbers assigned by the Cambridge Crystallographic
Data Centre (CCDC) to files containing structural information
archived by the CCDC.

### <a name="_database_code.depnum_ccdc_fiz"></a>\_database\_code.depnum\_ccdc\_fiz

Deposition numbers assigned by the Fachinformationszentrum
Karlsruhe (FIZ) to files containing structural information
archived by the Cambridge Crystallographic Data Centre (CCDC).

### <a name="_database_code.depnum_ccdc_journal"></a>\_database\_code.depnum\_ccdc\_journal

Deposition numbers assigned by various journals to files
containing structural information archived by the Cambridge
Crystallographic Data Centre (CCDC).

### <a name="_database_code.ICSD"></a>\_database\_code.ICSD

Code assigned by the Inorganic Crystal Structure Database.

### <a name="_database_code.MDF"></a>\_database\_code.MDF

Code assigned in the Metals Data File.

### <a name="_database_code.NBS"></a>\_database\_code.NBS

Code assigned by the NBS (NIST) Crystal Data Database.

### <a name="_database_code.PDB"></a>\_database\_code.PDB

Code assigned by the Protein Data Base.

### <a name="_database_code.PDF"></a>\_database\_code.PDF

Code assigned in the Powder Diffraction File.

## <a name="DATABASE_RELATED"></a>DATABASE\_RELATED

A category of items recording entries in databases that describe
the same or related data. Databases wishing to insert their own
canonical codes when archiving and delivering data blocks should
use items from the DATABASE category.


### <a name="_database_related.id"></a>\_database\_related.id

An identifer for this database reference

### <a name="_database_related.database_id"></a>\_database\_related.database\_id

An identifier for the database that contains the
related dataset.

### <a name="_database_related.entry_code"></a>\_database\_related.entry\_code

The code used by the database referred to in
[\_database\_related.database\_id](#_database_related.database_id) to identify the
related dataset.

### <a name="_database_related.relation"></a>\_database\_related.relation

The general relationship of the data in the data block
to the dataset referred to in the database.

Values:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>Identical</td><td>The dataset contents are identical</td></tr>
  <tr><td>Subset</td><td>The dataset contents are a proper subset of the contents of the data block</td></tr>
  <tr><td>Superset</td><td>The dataset contents include the contents of the data block</td></tr>
  <tr><td>Derived</td><td>The dataset contents are derivable from the contents of the data block</td></tr>
  <tr><td>Common</td><td>The dataset contents share a common source</td></tr>
</table>
### <a name="_database_related.special_details"></a>\_database\_related.special\_details

Information about the external dataset and relationship not encoded
elsewhere.

## <a name="DISPLAY"></a>DISPLAY

The CATEGORY of data items used to enumerate the display
parameters used in the discipline.

## <a name="DISPLAY_COLOUR"></a>DISPLAY\_COLOUR

The CATEGORY of data items used to enumerate the display
colour codes used in the discipline.

### <a name="_display_colour.blue"></a>\_display\_colour.blue

### <a name="_display_colour.green"></a>\_display\_colour.green

### <a name="_display_colour.hue"></a>\_display\_colour.hue

Colour hue as an enumerated code.

### <a name="_display_colour.red"></a>\_display\_colour.red

### <a name="_display_colour.RGB"></a>\_display\_colour.RGB

The red-green-blue intensities, bases 256, for each colour code.

## <a name="JOURNAL"></a>JOURNAL

Category of items recording details about the book-keeping
by the journal staff when processing a CIF submitted for
publication.  The creator of a CIF will not normally specify
these data items. 

### <a name="_journal.coden_ASTM"></a>\_journal.coden\_ASTM

ASTM code assigned to journal.

### <a name="_journal.coden_Cambridge"></a>\_journal.coden\_Cambridge

Cambridge Cryst. Data Centre code assigned to journal.

### <a name="_journal.data_validation_number"></a>\_journal.data\_validation\_number

Journal data items are defined by the journal staff.

### <a name="_journal.issue"></a>\_journal.issue

Issue identifier within the journal.

### <a name="_journal.language"></a>\_journal.language

Language of the publication.

### <a name="_journal.name_full"></a>\_journal.name\_full

Full name of the journal.

### <a name="_journal.page_first"></a>\_journal.page\_first

First page of the publication in the journal.

### <a name="_journal.page_last"></a>\_journal.page\_last

Last page of the publication in the journal.

### <a name="_journal.paper_category"></a>\_journal.paper\_category

Category of the publication in the journal.

### <a name="_journal.paper_doi"></a>\_journal.paper\_doi

DOI of the publication in the journal.

### <a name="_journal.suppl_publ_number"></a>\_journal.suppl\_publ\_number

Number of supplementary publication.

### <a name="_journal.suppl_publ_pages"></a>\_journal.suppl\_publ\_pages

Number of pages in the supplementary publication.

### <a name="_journal.validation_number"></a>\_journal.validation\_number

Data validation number assigned to journal.

### <a name="_journal.volume"></a>\_journal.volume

Volume number of the publication.

### <a name="_journal.year"></a>\_journal.year

Year of the publication.

## <a name="JOURNAL_COEDITOR"></a>JOURNAL\_COEDITOR

Category of items recording co-editor details.

### <a name="_journal_coeditor.address"></a>\_journal\_coeditor.address

The postal address of the coeditor.

### <a name="_journal_coeditor.code"></a>\_journal\_coeditor.code

The coeditor identifier.

### <a name="_journal_coeditor.email"></a>\_journal\_coeditor.email

The email address of the coeditor.

### <a name="_journal_coeditor.fax"></a>\_journal\_coeditor.fax

The fax number of the coeditor.

### <a name="_journal_coeditor.name"></a>\_journal\_coeditor.name

The name of the coeditor.

### <a name="_journal_coeditor.notes"></a>\_journal\_coeditor.notes

Notes on coeditor interaction wrt this publication.

### <a name="_journal_coeditor.phone"></a>\_journal\_coeditor.phone

The phone number of the coeditor.

## <a name="JOURNAL_DATE"></a>JOURNAL\_DATE

Category of items recording dates of publication processing.

### <a name="_journal_date.accepted"></a>\_journal\_date.accepted

Date the publication was accepted.

### <a name="_journal_date.from_coeditor"></a>\_journal\_date.from\_coeditor

Date the publication recieved from coeditor.

### <a name="_journal_date.printers_final"></a>\_journal\_date.printers\_final

Date the publication last sent to the printers.

### <a name="_journal_date.printers_first"></a>\_journal\_date.printers\_first

Date the publication first sent to the printers.

### <a name="_journal_date.proofs_in"></a>\_journal\_date.proofs\_in

Date the publication proofs recieved.

### <a name="_journal_date.proofs_out"></a>\_journal\_date.proofs\_out

Date the publication proofs sent out.

### <a name="_journal_date.recd_copyright"></a>\_journal\_date.recd\_copyright

Date completed copyright recieved.

### <a name="_journal_date.recd_electronic"></a>\_journal\_date.recd\_electronic

Date publication recieved electronically.

### <a name="_journal_date.recd_hard_copy"></a>\_journal\_date.recd\_hard\_copy

Date publication recieved as hard copy.

### <a name="_journal_date.to_coeditor"></a>\_journal\_date.to\_coeditor

Date the publication sent to the coeditor.

## <a name="JOURNAL_INDEX"></a>JOURNAL\_INDEX

Category of items describing publication indices.

### <a name="_journal_index.id"></a>\_journal\_index.id

Index number identifier of the [JOURNAL\_INDEX](#JOURNAL_INDEX) category.

### <a name="_journal_index.subterm"></a>\_journal\_index.subterm

Sub-term index assigned for the publication.

### <a name="_journal_index.term"></a>\_journal\_index.term

Term index assigned for the publication.

### <a name="_journal_index.type"></a>\_journal\_index.type

Type of index assigned for the publication.

Values:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>O</td><td>???????? formula ??????????????</td></tr>
  <tr><td>S</td><td>???????? structure description ???????</td></tr>
</table>
Default value: 'O'

## <a name="JOURNAL_TECHEDITOR"></a>JOURNAL\_TECHEDITOR

Category of items recording details of the technical editor
processing this publication.

### <a name="_journal_techeditor.address"></a>\_journal\_techeditor.address

Postal address of the technical editor for this publication.

### <a name="_journal_techeditor.code"></a>\_journal\_techeditor.code

Code of the technical editor for this publication.

### <a name="_journal_techeditor.email"></a>\_journal\_techeditor.email

Email address of the technical editor for this publication.

### <a name="_journal_techeditor.fax"></a>\_journal\_techeditor.fax

Fax number of the technical editor for this publication.

### <a name="_journal_techeditor.name"></a>\_journal\_techeditor.name

Name of the technical editor for this publication.

### <a name="_journal_techeditor.notes"></a>\_journal\_techeditor.notes

Notes of the technical editor for this publication.

### <a name="_journal_techeditor.phone"></a>\_journal\_techeditor.phone

Phone number of the technical editor for this publication.

## <a name="PUBL"></a>PUBL

Data items in the PUBL category are used when submitting a
manuscript for publication. They refer either to the paper as
a whole, or to specific named elements within a paper (such as
the title and abstract, or the Comment and Experimental
sections of Acta Crystallographica Section C). The data items
in the [PUBL\_BODY](#PUBL_BODY) category should be used for the textual
content of other submissions. Typically, each journal will
supply a list of the specific items it requires in its Notes
for Authors.

### <a name="_publ.contact_letter"></a>\_publ.contact\_letter

A letter submitted to the journal editor by the contact author.

## <a name="PUBL_AUTHOR"></a>PUBL\_AUTHOR

Category of data items recording the author information.

### <a name="_publ_author.address"></a>\_publ\_author.address

The address of a publication author. If there is more than one
author, this will be looped with [\_publ\_author.name](#_publ_author.name).

### <a name="_publ_author.email"></a>\_publ\_author.email

The e-mail address of a publication author. If there is more
than one author, this will be looped with [\_publ\_author.name](#_publ_author.name).
The format of e-mail addresses is given in Section 3.4, Address
Specification, of Internet Message Format, RFC 2822, P. Resnick
(Editor), Network Standards Group, April 2001.

### <a name="_publ_author.footnote"></a>\_publ\_author.footnote

A footnote accompanying an author&#39;s name in the list of authors
of a paper. Typically indicates sabbatical address, additional
affiliations or date of decease.

### <a name="_publ_author.id_iucr"></a>\_publ\_author.id\_iucr

Identifier in the IUCr contact database of a publication
author.  This identifier may be available from the World
Directory of Crystallographers ([http://wdc.iucr.org](http://wdc.iucr.org)).

### <a name="_publ_author.id_orcid"></a>\_publ\_author.id\_orcid

Identifier in the ORCID Registry of a publication
 author. ORCID is an open, non-profit, community-driven
 service to provide a registry of unique researcher
 identifiers ([http://orcid.org](http://orcid.org)).

### <a name="_publ_author.name"></a>\_publ\_author.name

The name of a publication author. If there are multiple authors,
this will be looped with [\_publ\_author.address](#_publ_author.address). The family
name(s), followed by a comma and including any dynastic
components, precedes the first names or initials.

### <a name="_publ_author.phone"></a>\_publ\_author.phone

Telephone number of the author submitting the manuscript and
data block.
 
The recommended style starts with the international dialing
prefix, followed by the area code in parentheses, followed by the
local number and any extension number prefixed by &#39;x&#39;,
with no spaces. The earlier convention of including
the international dialing prefix in parentheses is no longer
recommended.

## <a name="PUBL_BODY"></a>PUBL\_BODY

Data items in the [PUBL\_BODY](#PUBL_BODY) category permit labelling of
different text sections within the body of a submitted paper.
Note that these should not be used in a paper which has
a standard format with sections tagged by specific data names
(such as in Acta Crystallographica Section C). Typically,
each journal will supply a list of the specific items it
requires in its Notes for Authors.

### <a name="_publ_body.contents"></a>\_publ\_body.contents

A text section of a submitted paper.

### <a name="_publ_body.element"></a>\_publ\_body.element

The functional role of the associated text section.

Values:

* section
* subsection
* subsubsection
* appendix
* footnote

Default value: 'section'

### <a name="_publ_body.format"></a>\_publ\_body.format

Enumerated state indicating the appropriate typesetting
conventions for accented characters and special symbols
in the text section.

Values:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>ascii</td><td>no coding for special symbols</td></tr>
  <tr><td>cif</td><td>CIF convention</td></tr>
  <tr><td>latex</td><td>LaTeX</td></tr>
  <tr><td>rtf</td><td>Rich Text Format</td></tr>
  <tr><td>sgml</td><td>SGML (ISO 8879)</td></tr>
  <tr><td>tex</td><td>TeX</td></tr>
  <tr><td>troff</td><td>troff or nroff</td></tr>
</table>
Default value: 'cif'

### <a name="_publ_body.label"></a>\_publ\_body.label

Unigue identifier for each part of the body of the paper.

### <a name="_publ_body.title"></a>\_publ\_body.title

Title of the associated section of text.

## <a name="PUBL_CONTACT_AUTHOR"></a>PUBL\_CONTACT\_AUTHOR

Category of items describing contact author(s) details.

### <a name="_publ_contact_author.address"></a>\_publ\_contact\_author.address

The address of the author submitting the manuscript and
data block. This is the person contacted by the journal
editorial staff.

### <a name="_publ_contact_author.email"></a>\_publ\_contact\_author.email

E-mail address in a form recognizable to international networks.
The format of e-mail addresses is given in Section 3.4, Address
Specification, of Internet Message Format, RFC 2822, P. Resnick
(Editor), Network Standards Group, April 2001.

### <a name="_publ_contact_author.fax"></a>\_publ\_contact\_author.fax

Facsimile telephone number of the author submitting the manuscript
and data block.
The recommended style is the international dialing prefix, followed
by the area code in parentheses, followed by the local number with
no spaces. The earlier convention of including the international
dialing prefix in parentheses is no longer recommended.

### <a name="_publ_contact_author.id_iucr"></a>\_publ\_contact\_author.id\_iucr

Identifier in the IUCr contact database of the author submitting
the manuscript and datablock. This identifier may be available
from the World Directory of Crystallographers ([http://wdc.iucr.org](http://wdc.iucr.org)).

### <a name="_publ_contact_author.id_orcid"></a>\_publ\_contact\_author.id\_orcid

Identifier in the ORCID Registry of the author submitting
 the manuscript and data block. ORCID is an open, non-profit,
 community-driven service to provide a registry of unique
 researcher identifiers ([http://orcid.org](http://orcid.org)).

### <a name="_publ_contact_author.name"></a>\_publ\_contact\_author.name

The name of the author(s) submitting the manuscript and
data block. This is the person contacted by the journal
editorial staff.

### <a name="_publ_contact_author.phone"></a>\_publ\_contact\_author.phone

Telephone number of author submitting the manuscript and data block.
The recommended style is the international dialing prefix,
followed by the area code in parentheses, followed by the
local number and any extension number prefixed by &#39;x&#39;, with
no spaces. The earlier convention of including the international
dialing prefix in parentheses is no longer recommended.

## <a name="PUBL_MANUSCRIPT"></a>PUBL\_MANUSCRIPT

Category of items describing the publication manuscript.

### <a name="_publ_manuscript.creation"></a>\_publ\_manuscript.creation

A description of the wordprocessor package and computer used to
create the manuscript stored as [\_publ\_manuscript.processed](#_publ_manuscript.processed).

### <a name="_publ_manuscript.processed"></a>\_publ\_manuscript.processed

The full manuscript of a paper (excluding possibly the figures
and the tables) output in ASCII characters from a word processor.
Information about the generation of this data item must be
specified in the data item [\_publ\_manuscript.creation](#_publ_manuscript.creation).

### <a name="_publ_manuscript.text"></a>\_publ\_manuscript.text

The full manuscript of a paper (excluding figures and possibly
the tables) output as standard ASCII text.

## <a name="PUBL_MANUSCRIPT_INCL_EXTRA"></a>PUBL\_MANUSCRIPT\_INCL\_EXTRA

Category of data items that allow the authors of a manuscript to
submit for publication data names that should be added to the
standard request list employed by journal printing software.
Although these fields are primarily intended to identify CIF data
items that the author wishes to include in a published paper, they
can also be used to identify data names created so that non-CIF items
can be included in the publication. Note that \*.item names MUST be
enclosed in single quotes.

### <a name="_publ_manuscript_incl_extra.defn"></a>\_publ\_manuscript\_incl\_extra.defn

Yes/No flags whether the corresponding data item marked for inclusion
in a journal request list is a standard CIF definition or not.

Values:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>yes</td><td>include item in journal request list</td></tr>
  <tr><td>y</td><td>include item in journal request list</td></tr>
  <tr><td>no</td><td>exclude item in journal request list</td></tr>
  <tr><td>n</td><td>exclude item in journal request list</td></tr>
</table>
Default value: 'yes'

### <a name="_publ_manuscript_incl_extra.info"></a>\_publ\_manuscript\_incl\_extra.info

A short note indicating the reason why the author wishes the
corresponding data item marked for inclusion in the journal
request list to be published.

### <a name="_publ_manuscript_incl_extra.item"></a>\_publ\_manuscript\_incl\_extra.item

The data name (i.e. Tag) of a specific data item included in the
manuscript which is not normally requested by the journal. The values
of this item are the extra data names (which MUST be enclosed
in single quotes) that will be added to the journal request list.

## <a name="PUBL_REQUESTED"></a>PUBL\_REQUESTED

CATEGORY of data items that enable the author to make
specific requests to the journal office for processing.

### <a name="_publ_requested.category"></a>\_publ\_requested.category

The category of paper submitted. For submission to Acta
Crystallographica Section C or Acta Crystallographica
Section E, ONLY those codes indicated for use with those
journals should be used.

Values:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>AD</td><td>Addenda and Errata (Acta C, Acta E)</td></tr>
  <tr><td>CI</td><td>CIF-access paper - inorganic (Acta C) (no longer in use)</td></tr>
  <tr><td>CM</td><td>CIF-access paper - metal-organic (Acta C) (no longer in use)</td></tr>
  <tr><td>CO</td><td>CIF-access paper - organic (Acta C)  (no longer in use)</td></tr>
  <tr><td>EI</td><td>Electronic submission - inorganic (Acta E)</td></tr>
  <tr><td>EM</td><td>Electronic submission - metal-organic (Acta E)</td></tr>
  <tr><td>EO</td><td>Electronic submission - organic (Acta E)</td></tr>
  <tr><td>FA</td><td>Full article</td></tr>
  <tr><td>FI</td><td>Full submission - inorganic (Acta C)</td></tr>
  <tr><td>FM</td><td>Full submission - metal-organic (Acta C)</td></tr>
  <tr><td>FO</td><td>Full submission - organic (Acta C)</td></tr>
  <tr><td>GI</td><td>Research communications - inorganic compounds (Acta E)</td></tr>
  <tr><td>GM</td><td>Research communications - metal-organic compounds (Acta E)</td></tr>
  <tr><td>GO</td><td>Research communications - organic compounds (Acta E)</td></tr>
  <tr><td>HI</td><td>Data reports - inorganic compounds (Acta E)</td></tr>
  <tr><td>HM</td><td>Data reports - metal-organic compounds (Acta E)</td></tr>
  <tr><td>HO</td><td>Data reports - organic compounds (Acta E)</td></tr>
  <tr><td>QI</td><td>Inorganic compounds (Acta E)</td></tr>
  <tr><td>QM</td><td>Metal-organic compounds (Acta E)</td></tr>
  <tr><td>QO</td><td>Organic compounds (Acta E)</td></tr>
  <tr><td>SC</td><td>Short communication</td></tr>
</table>
Default value: 'FA'

### <a name="_publ_requested.coeditor_name"></a>\_publ\_requested.coeditor\_name

The name of the Co-editor whom the authors would like to
process the submitted manuscript.

### <a name="_publ_requested.journal"></a>\_publ\_requested.journal

Name of the journal to which the manuscript is being submitted.

## <a name="PUBL_SECTION"></a>PUBL\_SECTION

Manuscript section data if submitted in parts. see also
[\_publ\_manuscript.text](#_publ_manuscript.text) and [\_publ\_manuscript.processed](#_publ_manuscript.processed).
The [\_publ\_section.exptl\_prep](#_publ_section.exptl_prep), [\_publ\_section.exptl\_refinement](#_publ_section.exptl_refinement)
and [\_publ\_section.exptl\_solution](#_publ_section.exptl_solution) items are preferred for
separating the chemical preparation, refinement and structure
solution aspects of the experimental description.

### <a name="_publ_section.abstract"></a>\_publ\_section.abstract

The abstract of the submitted paper.

### <a name="_publ_section.acknowledgements"></a>\_publ\_section.acknowledgements

The acknowledgements section of the submitted paper.

### <a name="_publ_section.comment"></a>\_publ\_section.comment

The comment section of the submitted paper.

### <a name="_publ_section.discussion"></a>\_publ\_section.discussion

The discussion section of the submitted paper.

### <a name="_publ_section.experimental"></a>\_publ\_section.experimental

The experimental section of the submitted paper.

### <a name="_publ_section.exptl_prep"></a>\_publ\_section.exptl\_prep

The experimental preparation section of the submitted paper.

### <a name="_publ_section.exptl_refinement"></a>\_publ\_section.exptl\_refinement

The experimental refinement section of the submitted paper.

### <a name="_publ_section.exptl_solution"></a>\_publ\_section.exptl\_solution

The experimental solution section of the submitted paper.

### <a name="_publ_section.figure_captions"></a>\_publ\_section.figure\_captions

The figure captions of the submitted paper.

### <a name="_publ_section.introduction"></a>\_publ\_section.introduction

The introduction section of the submitted paper.

### <a name="_publ_section.keywords"></a>\_publ\_section.keywords

The keywords of the submitted paper.

### <a name="_publ_section.references"></a>\_publ\_section.references

The references section of the submitted paper.

### <a name="_publ_section.related_literature"></a>\_publ\_section.related\_literature

The related literature section of the submitted paper.

### <a name="_publ_section.synopsis"></a>\_publ\_section.synopsis

The synopsis of the submitted paper.

### <a name="_publ_section.table_legends"></a>\_publ\_section.table\_legends

The table legends of the submitted paper.

### <a name="_publ_section.title"></a>\_publ\_section.title

The full title of the submitted paper.

### <a name="_publ_section.title_footnote"></a>\_publ\_section.title\_footnote

Footnote (if any) to the title of the submitted paper.

## <a name="STRUCTURE"></a>STRUCTURE

The DICTIONARY group encompassing the CORE STRUCTURE data items defined
and used with in the Crystallographic Information Framework (CIF).

## <a name="ATOM"></a>ATOM

The CATEGORY of data items used to describe atomic information
used in crystallographic structure studies.

## <a name="ATOM_SITE"></a>ATOM\_SITE

The CATEGORY of data items used to describe atom site information
used in crystallographic structure studies.

### <a name="_atom_site.adp_type"></a>\_atom\_site.adp\_type

Code for type of atomic displacement parameters used for the site.

Values:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>Uani</td><td>anisotropic Uij</td></tr>
  <tr><td>Uiso</td><td>isotropic U</td></tr>
  <tr><td>Uovl</td><td>overall U</td></tr>
  <tr><td>Umpe</td><td>multipole expansion U</td></tr>
  <tr><td>Bani</td><td>anisotropic Bij</td></tr>
  <tr><td>Biso</td><td>isotropic B</td></tr>
  <tr><td>Bovl</td><td>overall B</td></tr>
</table>
### <a name="_atom_site.attached_hydrogens"></a>\_atom\_site.attached\_hydrogens

Number of hydrogen atoms attached to the atom at this site
excluding any H atoms for which coordinates (measured or calculated)
are given.

Examples:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>
2
  </td><td>water oxygen
  </td></tr>
  <tr><td>
1
  </td><td>hydroxyl oxygen
  </td></tr>
  <tr><td>
4
  </td><td>ammonium nitrogen
  </td></tr>
</table>
### <a name="_atom_site.B_equiv_geom_mean"></a>\_atom\_site.B\_equiv\_geom\_mean

Equivalent isotropic atomic displacement parameter, B(equiv),
in angstroms squared, calculated as the geometric mean of
the anisotropic atomic displacement parameters.
 
            B(equiv) = (B~i~ B~j~ B~k~)^1/3^
 
B~n~  = the principal components of the orthogonalised B^ij^
 
The IUCr Commission on Nomenclature recommends against the use
of B for reporting atomic displacement parameters. U, being
directly proportional to B, is preferred.

Units: angstrom\_squared

### <a name="_atom_site.B_equiv_geom_mean_su"></a>\_atom\_site.B\_equiv\_geom\_mean\_su

Standard Uncertainty value for the
Equivalent isotropic atomic displacement parameter, B(equiv),
in angstroms squared, calculated as the geometric mean of
the anisotropic atomic displacement parameters.

Units: angstrom\_squared

### <a name="_atom_site.B_iso_or_equiv"></a>\_atom\_site.B\_iso\_or\_equiv

Isotropic atomic displacement parameter, or equivalent isotropic
atomic displacement parameter, B(equiv), in angstroms squared,
calculated from anisotropic temperature factor parameters.
 
    B(equiv) = (1/3) sum~i~[sum~j~(B^ij^ a\*~i~ a\*~j~ a~i~ a~j~)]
 
a     = the real-space cell lengths
a\*    = the reciprocal-space cell lengths
B^ij^ = 8 pi^2^ U^ij^
Ref: Fischer, R. X. &amp; Tillmanns, E. (1988). Acta Cryst. C44, 775-776.
 
The IUCr Commission on Nomenclature recommends against the use
of B for reporting atomic displacement parameters. U, being
directly proportional to B, is preferred.

Units: angstrom\_squared

### <a name="_atom_site.B_iso_or_equiv_su"></a>\_atom\_site.B\_iso\_or\_equiv\_su

Standard Uncertainty value for the
Isotropic atomic displacement parameter, or equivalent isotropic
atomic displacement parameter, B(equiv), in angstroms squared,
calculated from anisotropic temperature factor parameters.

Units: angstrom\_squared

### <a name="_atom_site.calc_attached_atom"></a>\_atom\_site.calc\_attached\_atom

The [\_atom\_site.label](#_atom_site.label) of the atom site to which the &#39;geometry-
calculated&#39; atom site is attached.

### <a name="_atom_site.calc_flag"></a>\_atom\_site.calc\_flag

A standard code to signal if the site coordinates have been
determined from the intensities or calculated from the geometry
of surrounding sites, or have been assigned dummy coordinates.

Values:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>d</td><td>determined from diffraction measurements</td></tr>
  <tr><td>calc</td><td>calculated from molecular geometry</td></tr>
  <tr><td>c</td><td>abbreviation for &quot;calc&quot;</td></tr>
  <tr><td>dum</td><td>dummy site with meaningless coordinates</td></tr>
</table>
### <a name="_atom_site.Cartn_x"></a>\_atom\_site.Cartn\_x

### <a name="_atom_site.Cartn_x_su"></a>\_atom\_site.Cartn\_x\_su

### <a name="_atom_site.Cartn_xyz"></a>\_atom\_site.Cartn\_xyz

Vector of Cartesian (orthogonal angstrom) atom site coordinates.

### <a name="_atom_site.Cartn_y"></a>\_atom\_site.Cartn\_y

### <a name="_atom_site.Cartn_y_su"></a>\_atom\_site.Cartn\_y\_su

### <a name="_atom_site.Cartn_z"></a>\_atom\_site.Cartn\_z

### <a name="_atom_site.Cartn_z_su"></a>\_atom\_site.Cartn\_z\_su

### <a name="_atom_site.chemical_conn_number"></a>\_atom\_site.chemical\_conn\_number

This number links an atom site to the chemical connectivity list.
It must match a number specified by [\_chemical\_conn\_atom.number](#_chemical_conn_atom.number).

### <a name="_atom_site.constraints"></a>\_atom\_site.constraints

A description of the constraints applied to parameters at this
site during refinement. See also [\_atom\_site.refinement\_flags](#_atom_site.refinement_flags)
and [\_refine\_ls.number\_constraints](#_refine_ls.number_constraints).

### <a name="_atom_site.description"></a>\_atom\_site.description

A description of special aspects of this site. See also
[\_atom\_site.refinement\_flags](#_atom_site.refinement_flags).

### <a name="_atom_site.disorder_assembly"></a>\_atom\_site.disorder\_assembly

A code which identifies a cluster of atoms that show long range
positional disorder but are locally ordered. Within each such
cluster of atoms, [\_atom\_site.disorder\_group](#_atom_site.disorder_group) is used to identify
the sites that are simultaneously occupied. This field is only
needed if there is more than one cluster of disordered atoms
showing independent local order.

Examples:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>
A
  </td><td>disordered methyl assembly with groups 1 and 2
  </td></tr>
  <tr><td>
B
  </td><td>disordered sites related by a mirror
  </td></tr>
  <tr><td>
S
  </td><td>disordered sites independent of symmetry
  </td></tr>
</table>
### <a name="_atom_site.disorder_group"></a>\_atom\_site.disorder\_group

A code that identifies a group of positionally disordered atom
sites that are locally simultaneously occupied. Atoms that are
positionally disordered over two or more sites (e.g. the H
atoms of a methyl group that exists in two orientations) can
be assigned to two or more groups. Sites belonging to the same
group are simultaneously occupied, but those belonging to
different groups are not. A minus prefix (e.g. &quot;-1&quot;) is used to
indicate sites disordered about a special position.

Examples:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>
1
  </td><td>unique disordered site in group 1
  </td></tr>
  <tr><td>
2
  </td><td>unique disordered site in group 2
  </td></tr>
  <tr><td>
-1
  </td><td>symmetry-independent disordered site
  </td></tr>
</table>
### <a name="_atom_site.fract_x"></a>\_atom\_site.fract\_x

### <a name="_atom_site.fract_x_su"></a>\_atom\_site.fract\_x\_su

### <a name="_atom_site.fract_xyz"></a>\_atom\_site.fract\_xyz

Vector of atom site coordinates projected onto the crystal unit
cell as fractions of the cell lengths.

### <a name="_atom_site.fract_y"></a>\_atom\_site.fract\_y

### <a name="_atom_site.fract_y_su"></a>\_atom\_site.fract\_y\_su

### <a name="_atom_site.fract_z"></a>\_atom\_site.fract\_z

### <a name="_atom_site.fract_z_su"></a>\_atom\_site.fract\_z\_su

### <a name="_atom_site.label"></a>\_atom\_site.label

### <a name="_atom_site.label_component_0"></a>\_atom\_site.label\_component\_0

### <a name="_atom_site.label_component_1"></a>\_atom\_site.label\_component\_1

### <a name="_atom_site.label_component_2"></a>\_atom\_site.label\_component\_2

### <a name="_atom_site.label_component_3"></a>\_atom\_site.label\_component\_3

### <a name="_atom_site.label_component_4"></a>\_atom\_site.label\_component\_4

### <a name="_atom_site.label_component_5"></a>\_atom\_site.label\_component\_5

### <a name="_atom_site.label_component_6"></a>\_atom\_site.label\_component\_6

### <a name="_atom_site.occupancy"></a>\_atom\_site.occupancy

The fraction of the atom type present at this site.
The sum of the occupancies of all the atom types at this site
may not significantly exceed 1.0 unless it is a dummy site. The
value must lie in the 99.97% Gaussian confidence interval
-3u =&lt; x =&lt; 1 + 3u. The \_enumeration.range of 0.0:1.0 is thus
correctly interpreted as meaning (0.0 - 3u) =&lt; x =&lt; (1.0 + 3u).

Units: none

### <a name="_atom_site.occupancy_su"></a>\_atom\_site.occupancy\_su

Standard Uncertainty value for the
The fraction of the atom type present at this site.

Units: none

### <a name="_atom_site.refinement_flags"></a>\_atom\_site.refinement\_flags

A concatenated series of single-letter codes which indicate the
refinement restraints or constraints applied to this site. This
item should not be used. It has been replaced by 
[\_atom\_site.refinement\_flags\_posn](#_atom_site.refinement_flags_posn), \_adp and \_occupancy. It is
retained in this dictionary only to provide compatibility with
legacy CIFs.

Values:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>S</td><td>special position constraint on site</td></tr>
  <tr><td>G</td><td>rigid group refinement of site</td></tr>
  <tr><td>R</td><td>riding-atom site attached to non-riding atom</td></tr>
  <tr><td>D</td><td>distance or angle restraint on site</td></tr>
  <tr><td>T</td><td>thermal displacement constraints</td></tr>
  <tr><td>U</td><td>Uiso or Uij restraint (rigid bond)</td></tr>
  <tr><td>P</td><td>partial occupancy constraint</td></tr>
  <tr><td>.</td><td>no refinement constraints</td></tr>
</table>
### <a name="_atom_site.refinement_flags_adp"></a>\_atom\_site.refinement\_flags\_adp

A code which indicates the refinement restraints or constraints
applied to the atomic displacement parameters of this site.

Values:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>.</td><td>no constraints on atomic displacement parameters</td></tr>
  <tr><td>T</td><td>special-position constraints on atomic displacement parameters</td></tr>
  <tr><td>U</td><td>Uiso or Uij restraint (rigid bond)</td></tr>
  <tr><td>TU</td><td>both constraints applied</td></tr>
</table>
### <a name="_atom_site.refinement_flags_occupancy"></a>\_atom\_site.refinement\_flags\_occupancy

A code which indicates the refinement restraints or constraints
applied to the occupancy of this site.

Values:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>.</td><td>no constraints on site-occupancy parameters</td></tr>
  <tr><td>P</td><td>site-occupancy constraint</td></tr>
</table>
### <a name="_atom_site.refinement_flags_posn"></a>\_atom\_site.refinement\_flags\_posn

A code which indicates the refinement restraints or constraints
applied to the positional coordinates of this site.

Values:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>.</td><td>no constraints on positional coordinates</td></tr>
  <tr><td>D</td><td>distance or angle restraint on positional coordinates</td></tr>
  <tr><td>G</td><td>rigid-group refinement of positional coordinates</td></tr>
  <tr><td>R</td><td>riding-atom site attached to non-riding atom</td></tr>
  <tr><td>S</td><td>special-position constraint on positional coordinates</td></tr>
  <tr><td>DG</td><td>combination of the above constraints</td></tr>
  <tr><td>DR</td><td>combination of the above constraints</td></tr>
  <tr><td>DS</td><td>combination of the above constraints</td></tr>
  <tr><td>GR</td><td>combination of the above constraints</td></tr>
  <tr><td>GS</td><td>combination of the above constraints</td></tr>
  <tr><td>RS</td><td>combination of the above constraints</td></tr>
  <tr><td>DGR</td><td>combination of the above constraints</td></tr>
  <tr><td>DGS</td><td>combination of the above constraints</td></tr>
  <tr><td>DRS</td><td>combination of the above constraints</td></tr>
  <tr><td>GRS</td><td>combination of the above constraints</td></tr>
  <tr><td>DGRS</td><td>combination of the above constraints</td></tr>
</table>
### <a name="_atom_site.restraints"></a>\_atom\_site.restraints

A description of restraints applied to specific parameters at
this site during refinement. See also [\_atom\_site.refinement\_flags](#_atom_site.refinement_flags)
and [\_refine\_ls.number\_restraints](#_refine_ls.number_restraints).

### <a name="_atom_site.site_symmetry_multiplicity"></a>\_atom\_site.site\_symmetry\_multiplicity

The number of different sites that are generated by the
application of the space-group symmetry to the coordinates
given for this site. It is equal to the multiplicity given
for this Wyckoff site in International Tables for Cryst.
Vol. A (2002). It is equal to the multiplicity of the general
position divided by the order of the site symmetry given in
[\_atom\_site.site\_symmetry\_order](#_atom_site.site_symmetry_order).

### <a name="_atom_site.site_symmetry_order"></a>\_atom\_site.site\_symmetry\_order

The number of times application of the crystallographic symmetry
to the coordinates for this site generates the same coordinates.
That is:
        multiplicity of the general position
        ------------------------------------
        [\_atom\_site.site\_symmetry\_multiplicity](#_atom_site.site_symmetry_multiplicity)

### <a name="_atom_site.tensor_beta"></a>\_atom\_site.tensor\_beta

The symmetric anisotropic atomic displacement tensor beta[I,J]
appears in a structure factor expression as:
 
t = exp -[ beta11 h h + ............ 2 beta23 k l ]
 
It is related to the adp matrices U(IJ) and B(IJ) as follows:
 
t = exp -2pi\*\*2 ( U11    h h a\* a\* + ...... 2 U23    k l b\* c\* )
t = exp - 0.25  ( B11    h h a\* a\* + ...... 2 B23    k l b\* c\* )

### <a name="_atom_site.type_symbol"></a>\_atom\_site.type\_symbol

A code to identify the atom specie(s) occupying this site.
This code must match a corresponding [\_atom\_type.symbol](#_atom_type.symbol). The
specification of this code is optional if component\_0 of the
[\_atom\_site.label](#_atom_site.label) is used for this purpose. See [\_atom\_type.symbol](#_atom_type.symbol).

### <a name="_atom_site.U_equiv_geom_mean"></a>\_atom\_site.U\_equiv\_geom\_mean

Equivalent isotropic atomic displacement parameter, U(equiv),
in angstroms squared, calculated as the geometric mean of
the anisotropic atomic displacement parameters.
 
           U(equiv) = (U~i~ U~j~ U~k~)^1/3^
 
U~n~ = the principal components of the orthogonalised U^ij^

Units: angstrom\_squared

### <a name="_atom_site.U_equiv_geom_mean_su"></a>\_atom\_site.U\_equiv\_geom\_mean\_su

Standard uncertainty values (esds) of the U(equiv).

Units: angstrom\_squared

### <a name="_atom_site.U_iso_or_equiv"></a>\_atom\_site.U\_iso\_or\_equiv

Isotropic atomic displacement parameter, or equivalent isotropic
atomic  displacement parameter, U(equiv), in angstroms squared,
calculated from anisotropic atomic displacement  parameters.
 
   U(equiv) = (1/3) sum~i~[sum~j~(U^ij^ a\*~i~ a\*~j~ a~i~ a~j~)]
 
a  = the real-space cell lengths
a\* = the reciprocal-space cell lengths
Ref: Fischer, R. X. &amp; Tillmanns, E. (1988). Acta Cryst. C44, 775-776.

Units: angstrom\_squared

### <a name="_atom_site.U_iso_or_equiv_su"></a>\_atom\_site.U\_iso\_or\_equiv\_su

Standard uncertainty values (esds) of the U(iso) or U(equiv).

Units: angstrom\_squared

### <a name="_atom_site.Wyckoff_symbol"></a>\_atom\_site.Wyckoff\_symbol

The Wyckoff symbol (letter) as listed in the space-group section
of International Tables for Crystallography, Vol. A (1987).

## <a name="ATOM_SITE_ANISO"></a>ATOM\_SITE\_ANISO

The CATEGORY of data items used to describe the anisotropic
thermal parameters of the atomic sites in a crystal structure.

### <a name="_atom_site_aniso.B_11"></a>\_atom\_site\_aniso.B\_11

### <a name="_atom_site_aniso.B_11_su"></a>\_atom\_site\_aniso.B\_11\_su

### <a name="_atom_site_aniso.B_12"></a>\_atom\_site\_aniso.B\_12

### <a name="_atom_site_aniso.B_12_su"></a>\_atom\_site\_aniso.B\_12\_su

### <a name="_atom_site_aniso.B_13"></a>\_atom\_site\_aniso.B\_13

### <a name="_atom_site_aniso.B_13_su"></a>\_atom\_site\_aniso.B\_13\_su

### <a name="_atom_site_aniso.B_22"></a>\_atom\_site\_aniso.B\_22

### <a name="_atom_site_aniso.B_22_su"></a>\_atom\_site\_aniso.B\_22\_su

### <a name="_atom_site_aniso.B_23"></a>\_atom\_site\_aniso.B\_23

### <a name="_atom_site_aniso.B_23_su"></a>\_atom\_site\_aniso.B\_23\_su

### <a name="_atom_site_aniso.B_33"></a>\_atom\_site\_aniso.B\_33

### <a name="_atom_site_aniso.B_33_su"></a>\_atom\_site\_aniso.B\_33\_su

### <a name="_atom_site_aniso.label"></a>\_atom\_site\_aniso.label

Anisotropic atomic displacement parameters are usually looped in
a separate list. If this is the case, this code must match the
[\_atom\_site.label](#_atom_site.label) of the associated atom in the atom coordinate
list and conform with the same rules described in [\_atom\_site.label](#_atom_site.label).

### <a name="_atom_site_aniso.matrix_B"></a>\_atom\_site\_aniso.matrix\_B

The symmetric anisotropic atomic displacement matrix B.

### <a name="_atom_site_aniso.matrix_U"></a>\_atom\_site\_aniso.matrix\_U

The symmetric anisotropic atomic displacement matrix U.

### <a name="_atom_site_aniso.ratio"></a>\_atom\_site\_aniso.ratio

Ratio of the maximum to minimum eigenvalues of the atomic
displacement (thermal) ellipsoids.

Units: none

### <a name="_atom_site_aniso.type_symbol"></a>\_atom\_site\_aniso.type\_symbol

This [\_atom\_type.symbol](#_atom_type.symbol) code links the anisotropic atom parameters to
the atom type data associated with this site and must match one of
the [\_atom\_type.symbol](#_atom_type.symbol) codes in this list.

### <a name="_atom_site_aniso.U_11"></a>\_atom\_site\_aniso.U\_11

### <a name="_atom_site_aniso.U_11_su"></a>\_atom\_site\_aniso.U\_11\_su

### <a name="_atom_site_aniso.U_12"></a>\_atom\_site\_aniso.U\_12

### <a name="_atom_site_aniso.U_12_su"></a>\_atom\_site\_aniso.U\_12\_su

### <a name="_atom_site_aniso.U_13"></a>\_atom\_site\_aniso.U\_13

### <a name="_atom_site_aniso.U_13_su"></a>\_atom\_site\_aniso.U\_13\_su

### <a name="_atom_site_aniso.U_22"></a>\_atom\_site\_aniso.U\_22

### <a name="_atom_site_aniso.U_22_su"></a>\_atom\_site\_aniso.U\_22\_su

### <a name="_atom_site_aniso.U_23"></a>\_atom\_site\_aniso.U\_23

### <a name="_atom_site_aniso.U_23_su"></a>\_atom\_site\_aniso.U\_23\_su

### <a name="_atom_site_aniso.U_33"></a>\_atom\_site\_aniso.U\_33

### <a name="_atom_site_aniso.U_33_su"></a>\_atom\_site\_aniso.U\_33\_su

## <a name="ATOM_SITES"></a>ATOM\_SITES

The CATEGORY of data items used to describe information which applies
to all atom sites in a crystal structure.

### <a name="_atom_sites.solution_hydrogens"></a>\_atom\_sites.solution\_hydrogens

Codes which identify the methods used to locate the initial
atom sites. The \*\_primary code identifies how the first
atom sites were determined; the \*\_secondary code identifies
how the remaining non-hydrogen sites were located; and the
\*\_hydrogens code identifies how the hydrogen sites were located.
 
Ref: Sheldrick, G. M., Hauptman, H. A., Weeks, C. M.,
     Miller, R. and Us\&#39;on, I. (2001). Ab initio phasing.
     In International Tables for Crystallography,
     Vol. F. Crystallography of biological macromolecules,
     edited by M. G. Rossmann and E. Arnold, ch. 16.1.
     Dordrecht: Kluwer Academic Publishers.

Values:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>difmap</td><td>difference Fourier map</td></tr>
  <tr><td>vecmap</td><td>real-space vector search</td></tr>
  <tr><td>heavy</td><td>heavy-atom method</td></tr>
  <tr><td>direct</td><td>structure-invariant direct methods</td></tr>
  <tr><td>geom</td><td>inferred from neighbouring sites</td></tr>
  <tr><td>disper</td><td>anomalous-dispersion techniques</td></tr>
  <tr><td>isomor</td><td>isomorphous structure methods</td></tr>
  <tr><td>mixed</td><td>a mixture of &quot;geom&quot; and &quot;difmap&quot;</td></tr>
  <tr><td>notdet</td><td>coordinates were not determined</td></tr>
  <tr><td>dual</td><td>dual-space method (Sheldrick et al., 2001)</td></tr>
  <tr><td>iterative</td><td>iterative e.g. charge flipping [Oszl\&#39;anyi, G.
                  and S\&quot;uto, A. (2004). Acta Cryst. A60, 134-141]</td></tr>
  <tr><td>other</td><td>a method not included elsewhere in this list</td></tr>
</table>
### <a name="_atom_sites.solution_primary"></a>\_atom\_sites.solution\_primary

Codes which identify the methods used to locate the initial
atom sites. The \*\_primary code identifies how the first
atom sites were determined; the \*\_secondary code identifies
how the remaining non-hydrogen sites were located; and the
\*\_hydrogens code identifies how the hydrogen sites were located.
 
Ref: Sheldrick, G. M., Hauptman, H. A., Weeks, C. M.,
     Miller, R. and Us\&#39;on, I. (2001). Ab initio phasing.
     In International Tables for Crystallography,
     Vol. F. Crystallography of biological macromolecules,
     edited by M. G. Rossmann and E. Arnold, ch. 16.1.
     Dordrecht: Kluwer Academic Publishers.

Values:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>difmap</td><td>difference Fourier map</td></tr>
  <tr><td>vecmap</td><td>real-space vector search</td></tr>
  <tr><td>heavy</td><td>heavy-atom method</td></tr>
  <tr><td>direct</td><td>structure-invariant direct methods</td></tr>
  <tr><td>geom</td><td>inferred from neighbouring sites</td></tr>
  <tr><td>disper</td><td>anomalous-dispersion techniques</td></tr>
  <tr><td>isomor</td><td>isomorphous structure methods</td></tr>
  <tr><td>notdet</td><td>coordinates were not determined</td></tr>
  <tr><td>dual</td><td>dual-space method (Sheldrick et al., 2001)</td></tr>
  <tr><td>iterative</td><td>iterative e.g. charge flipping [Oszl\&#39;anyi, G.
                  and S\&quot;uto, A. (2004). Acta Cryst. A60, 134-141]</td></tr>
  <tr><td>other</td><td>a method not included elsewhere in this list</td></tr>
</table>
### <a name="_atom_sites.solution_secondary"></a>\_atom\_sites.solution\_secondary

Codes which identify the methods used to locate the initial
atom sites. The \*\_primary code identifies how the first
atom sites were determined; the \*\_secondary code identifies
how the remaining non-hydrogen sites were located; and the
\*\_hydrogens code identifies how the hydrogen sites were located.
 
Ref: Sheldrick, G. M., Hauptman, H. A., Weeks, C. M.,
     Miller, R. and Us\&#39;on, I. (2001). Ab initio phasing.
     In International Tables for Crystallography,
     Vol. F. Crystallography of biological macromolecules,
     edited by M. G. Rossmann and E. Arnold, ch. 16.1.
     Dordrecht: Kluwer Academic Publishers.

Values:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>difmap</td><td>difference Fourier map</td></tr>
  <tr><td>vecmap</td><td>real-space vector search</td></tr>
  <tr><td>heavy</td><td>heavy-atom method</td></tr>
  <tr><td>direct</td><td>structure-invariant direct methods</td></tr>
  <tr><td>geom</td><td>inferred from neighbouring sites</td></tr>
  <tr><td>disper</td><td>anomalous-dispersion techniques</td></tr>
  <tr><td>isomor</td><td>isomorphous structure methods</td></tr>
  <tr><td>notdet</td><td>coordinates were not determined</td></tr>
  <tr><td>dual</td><td>dual-space method (Sheldrick et al., 2001)</td></tr>
  <tr><td>iterative</td><td>iterative e.g. charge flipping [Oszl\&#39;anyi, G.
                  and S\&quot;uto, A. (2004). Acta Cryst. A60, 134-141]</td></tr>
  <tr><td>other</td><td>a method not included elsewhere in this list</td></tr>
</table>
### <a name="_atom_sites.special_details"></a>\_atom\_sites.special\_details

Information about atomic coordinates not coded elsewhere in the CIF.

## <a name="ATOM_SITES_CARTN_TRANSFORM"></a>ATOM\_SITES\_CARTN\_TRANSFORM

The CATEGORY of data items used to describe the matrix elements
used to transform Cartesion coordinates into fractional coordinates
of all atom sites in a crystal structure.

### <a name="_atom_sites_Cartn_transform.axes"></a>\_atom\_sites\_Cartn\_transform.axes

Description of the relative alignment of the crystal cell axes to the
Cartesian orthogonal axes as applied in the transformation matrix
[\_atom\_sites\_Cartn\_transform.matrix](#_atom_sites_Cartn_transform.matrix).

### <a name="_atom_sites_Cartn_transform.mat_11"></a>\_atom\_sites\_Cartn\_transform.mat\_11

### <a name="_atom_sites_Cartn_transform.mat_12"></a>\_atom\_sites\_Cartn\_transform.mat\_12

### <a name="_atom_sites_Cartn_transform.mat_13"></a>\_atom\_sites\_Cartn\_transform.mat\_13

### <a name="_atom_sites_Cartn_transform.mat_21"></a>\_atom\_sites\_Cartn\_transform.mat\_21

### <a name="_atom_sites_Cartn_transform.mat_22"></a>\_atom\_sites\_Cartn\_transform.mat\_22

### <a name="_atom_sites_Cartn_transform.mat_23"></a>\_atom\_sites\_Cartn\_transform.mat\_23

### <a name="_atom_sites_Cartn_transform.mat_31"></a>\_atom\_sites\_Cartn\_transform.mat\_31

### <a name="_atom_sites_Cartn_transform.mat_32"></a>\_atom\_sites\_Cartn\_transform.mat\_32

### <a name="_atom_sites_Cartn_transform.mat_33"></a>\_atom\_sites\_Cartn\_transform.mat\_33

### <a name="_atom_sites_Cartn_transform.matrix"></a>\_atom\_sites\_Cartn\_transform.matrix

Matrix used to transform fractional coordinates in the [ATOM\_SITE](#ATOM_SITE)
category to Cartesian  coordinates. The axial alignments of this
transformation are described in [\_atom\_sites\_Cartn\_transform.axes](#_atom_sites_Cartn_transform.axes).
The 3 x 1 translation is defined in [\_atom\_sites\_Cartn\_transform.vector](#_atom_sites_Cartn_transform.vector).
 
  x&#39;                   |11 12 13|     x                  | 1 |
( y&#39; ) Cartesian   =   |21 22 23| \* ( y ) fractional  + v| 2 |
  z&#39;                   |31 32 33|     z                  | 3 |
 
The default transformation matrix uses Rollet&#39;s axial
assignments with cell vectors a,b,c aligned with orthogonal
axes X,Y,Z so that c||Z and b in plane YZ.

### <a name="_atom_sites_Cartn_transform.vec_1"></a>\_atom\_sites\_Cartn\_transform.vec\_1

### <a name="_atom_sites_Cartn_transform.vec_2"></a>\_atom\_sites\_Cartn\_transform.vec\_2

### <a name="_atom_sites_Cartn_transform.vec_3"></a>\_atom\_sites\_Cartn\_transform.vec\_3

### <a name="_atom_sites_Cartn_transform.vector"></a>\_atom\_sites\_Cartn\_transform.vector

The 3x1 translation is used with [\_atom\_sites\_Cartn\_transform.matrix](#_atom_sites_Cartn_transform.matrix)
used to transform fractional coordinates to Cartesian  coordinates.
The axial alignments of this transformation are described in
[\_atom\_sites\_Cartn\_transform.axes](#_atom_sites_Cartn_transform.axes).

## <a name="ATOM_SITES_FRACT_TRANSFORM"></a>ATOM\_SITES\_FRACT\_TRANSFORM

The CATEGORY of data items used to describe the matrix elements
used to transform Cartesion coordinates into fractional coordinates
of all atom sites in a crystal structure.

### <a name="_atom_sites_fract_transform.axes"></a>\_atom\_sites\_fract\_transform.axes

Description of the relative alignment of the crystal cell axes to the
Cartesian orthogonal axes as applied in the transformation matrix
[\_atom\_sites\_fract\_transform.matrix](#_atom_sites_fract_transform.matrix).

### <a name="_atom_sites_fract_transform.mat_11"></a>\_atom\_sites\_fract\_transform.mat\_11

### <a name="_atom_sites_fract_transform.mat_12"></a>\_atom\_sites\_fract\_transform.mat\_12

### <a name="_atom_sites_fract_transform.mat_13"></a>\_atom\_sites\_fract\_transform.mat\_13

### <a name="_atom_sites_fract_transform.mat_21"></a>\_atom\_sites\_fract\_transform.mat\_21

### <a name="_atom_sites_fract_transform.mat_22"></a>\_atom\_sites\_fract\_transform.mat\_22

### <a name="_atom_sites_fract_transform.mat_23"></a>\_atom\_sites\_fract\_transform.mat\_23

### <a name="_atom_sites_fract_transform.mat_31"></a>\_atom\_sites\_fract\_transform.mat\_31

### <a name="_atom_sites_fract_transform.mat_32"></a>\_atom\_sites\_fract\_transform.mat\_32

### <a name="_atom_sites_fract_transform.mat_33"></a>\_atom\_sites\_fract\_transform.mat\_33

### <a name="_atom_sites_fract_transform.matrix"></a>\_atom\_sites\_fract\_transform.matrix

Matrix used to transform fractional coordinates in the [ATOM\_SITE](#ATOM_SITE)
category to Cartesian  coordinates. The axial alignments of this
transformation are described in [\_atom\_sites\_fract\_transform.axes](#_atom_sites_fract_transform.axes).
The 3 x 1 translation is defined in [\_atom\_sites\_fract\_transform.vector](#_atom_sites_fract_transform.vector).
 
  x&#39;                   |11 12 13|     x                  | 1 |
( y&#39; )fractional = mat |21 22 23| \* ( y ) Cartesian + vec| 2 |
  z&#39;                   |31 32 33|     z                  | 3 |
 
The default transformation matrix uses Rollet&#39;s axial
assignments with cell vectors a,b,c aligned with orthogonal
axes X,Y,Z so that c||Z and b in plane YZ.

### <a name="_atom_sites_fract_transform.vec_1"></a>\_atom\_sites\_fract\_transform.vec\_1

### <a name="_atom_sites_fract_transform.vec_2"></a>\_atom\_sites\_fract\_transform.vec\_2

### <a name="_atom_sites_fract_transform.vec_3"></a>\_atom\_sites\_fract\_transform.vec\_3

### <a name="_atom_sites_fract_transform.vector"></a>\_atom\_sites\_fract\_transform.vector

The 3x1 translation is used with [\_atom\_sites\_fract\_transform.matrix](#_atom_sites_fract_transform.matrix)
used to transform Cartesian coordinates to fractional  coordinates.
The axial alignments of this transformation are described in
[\_atom\_sites\_fract\_transform.axes](#_atom_sites_fract_transform.axes).

## <a name="ATOM_TYPE"></a>ATOM\_TYPE

The CATEGORY of data items used to describe atomic type information
used in crystallographic structure studies.

### <a name="_atom_type.analytical_mass_percent"></a>\_atom\_type.analytical\_mass\_percent

Mass percentage of this atom type derived from chemical analysis.

Units: none

### <a name="_atom_type.atomic_mass"></a>\_atom\_type.atomic\_mass

Mass of this atom type.

Units: dalton

### <a name="_atom_type.atomic_number"></a>\_atom\_type.atomic\_number

Atomic number of this atom type.

### <a name="_atom_type.description"></a>\_atom\_type.description

A description of the atom(s) designated by this atom type. In
most cases this will be the element name and oxidation state of
a single atom  species. For disordered or nonstoichiometric
structures it will describe a combination of atom species.

### <a name="_atom_type.display_colour"></a>\_atom\_type.display\_colour

The display colour assigned to this atom type. Note that the
possible colours are enumerated in the display\_colour list
category of items.

### <a name="_atom_type.electron_count"></a>\_atom\_type.electron\_count

Number of electrons in this atom type.

### <a name="_atom_type.element_symbol"></a>\_atom\_type.element\_symbol

Element symbol for of this atom type. The default value is extracted
from the ion-to-element enumeration\_default list using the index
value of [\_atom\_type.symbol](#_atom_type.symbol).

### <a name="_atom_type.key"></a>\_atom\_type.key

Value is a unique key to a set of [ATOM\_TYPE](#ATOM_TYPE) items
in a looped list.

### <a name="_atom_type.number_in_cell"></a>\_atom\_type.number\_in\_cell

Total number of atoms of this atom type in the unit cell.

Units: none

### <a name="_atom_type.oxidation_number"></a>\_atom\_type.oxidation\_number

Formal oxidation state of this atom type in the structure.

### <a name="_atom_type.radius_bond"></a>\_atom\_type.radius\_bond

The effective intra-molecular bonding radius of this atom type.

Units: angstroms

### <a name="_atom_type.radius_contact"></a>\_atom\_type.radius\_contact

The effective inter-molecular bonding radius of this atom type.

Units: angstroms

### <a name="_atom_type.symbol"></a>\_atom\_type.symbol

The identity of the atom specie(s) representing this atom type.
Normally this code is the element symbol followed by the charge
if there is one. The symbol may be composed of any character except
an underline or a blank, with the proviso that digits designate an
oxidation state and must be followed by a + or - character.

## <a name="ATOM_TYPE_SCAT"></a>ATOM\_TYPE\_SCAT

The CATEGORY of data items used to describe atomic scattering
information used in crystallographic structure studies.

### <a name="_atom_type_scat.Cromer_Mann_a1"></a>\_atom\_type\_scat.Cromer\_Mann\_a1

### <a name="_atom_type_scat.Cromer_Mann_a2"></a>\_atom\_type\_scat.Cromer\_Mann\_a2

### <a name="_atom_type_scat.Cromer_Mann_a3"></a>\_atom\_type\_scat.Cromer\_Mann\_a3

### <a name="_atom_type_scat.Cromer_Mann_a4"></a>\_atom\_type\_scat.Cromer\_Mann\_a4

### <a name="_atom_type_scat.Cromer_Mann_b1"></a>\_atom\_type\_scat.Cromer\_Mann\_b1

### <a name="_atom_type_scat.Cromer_Mann_b2"></a>\_atom\_type\_scat.Cromer\_Mann\_b2

### <a name="_atom_type_scat.Cromer_Mann_b3"></a>\_atom\_type\_scat.Cromer\_Mann\_b3

### <a name="_atom_type_scat.Cromer_Mann_b4"></a>\_atom\_type\_scat.Cromer\_Mann\_b4

### <a name="_atom_type_scat.Cromer_Mann_c"></a>\_atom\_type\_scat.Cromer\_Mann\_c

### <a name="_atom_type_scat.Cromer_Mann_coeffs"></a>\_atom\_type\_scat.Cromer\_Mann\_coeffs

The set of Cromer-Mann coefficients for generating X-ray scattering
factors. [ a1, b1, a2, b2, a3, b3, a4, b4, c]
Ref: International Tables for Crystallography, Vol. C
        (1991) Table 6.1.1.4

Units: none

### <a name="_atom_type_scat.dispersion"></a>\_atom\_type\_scat.dispersion

The anomalous dispersion scattering factor in its complex form
for this atom type and radiation by [\_diffrn\_radiation\_wavelength.value](#_diffrn_radiation_wavelength.value)

Units: none

### <a name="_atom_type_scat.dispersion_imag"></a>\_atom\_type\_scat.dispersion\_imag

The imaginary component of the anomalous dispersion scattering factors
for this atom type and radiation by [\_diffrn\_radiation\_wavelength.value](#_diffrn_radiation_wavelength.value)

Units: none

### <a name="_atom_type_scat.dispersion_imag_cu"></a>\_atom\_type\_scat.dispersion\_imag\_cu

The imaginary component of the anomalous dispersion scattering factors
for this atom type and Cu K alpha radiation

Units: none

### <a name="_atom_type_scat.dispersion_imag_mo"></a>\_atom\_type\_scat.dispersion\_imag\_mo

The imaginary component of the anomalous dispersion scattering factors
for this atom type and Mo K alpha radiation

Units: none

### <a name="_atom_type_scat.dispersion_real"></a>\_atom\_type\_scat.dispersion\_real

The real component of the anomalous dispersion scattering factors
for this atom type and radiation by [\_diffrn\_radiation\_wavelength.value](#_diffrn_radiation_wavelength.value)

Units: none

### <a name="_atom_type_scat.dispersion_real_cu"></a>\_atom\_type\_scat.dispersion\_real\_cu

The real component of the anomalous dispersion scattering factors
for this atom type and Cu K alpha radiation

Units: none

### <a name="_atom_type_scat.dispersion_real_mo"></a>\_atom\_type\_scat.dispersion\_real\_mo

The real component of the anomalous dispersion scattering factors
for this atom type and Mo K alpha radiation

Units: none

### <a name="_atom_type_scat.dispersion_source"></a>\_atom\_type\_scat.dispersion\_source

Reference to source of real and imaginary dispersion
corrections for scattering factors used for this atom type.

### <a name="_atom_type_scat.hi_ang_Fox_c0"></a>\_atom\_type\_scat.hi\_ang\_Fox\_c0

### <a name="_atom_type_scat.hi_ang_Fox_c1"></a>\_atom\_type\_scat.hi\_ang\_Fox\_c1

### <a name="_atom_type_scat.hi_ang_Fox_c2"></a>\_atom\_type\_scat.hi\_ang\_Fox\_c2

### <a name="_atom_type_scat.hi_ang_Fox_c3"></a>\_atom\_type\_scat.hi\_ang\_Fox\_c3

### <a name="_atom_type_scat.hi_ang_Fox_coeffs"></a>\_atom\_type\_scat.hi\_ang\_Fox\_coeffs

The set of Fox et al. coefficients for generating high angle
X-ray scattering factors. [ c0, c1, c2, c3 ]
Ref: International Tables for Crystallography, Vol. C
        (1991) Table 6.1.1.5

Units: none

### <a name="_atom_type_scat.length_neutron"></a>\_atom\_type\_scat.length\_neutron

The bound coherent scattering length for the atom type at the
isotopic composition used for the diffraction experiment.

Units: femtometres

### <a name="_atom_type_scat.source"></a>\_atom\_type\_scat.source

Reference to source of scattering factors used for this atom type.

### <a name="_atom_type_scat.symbol"></a>\_atom\_type\_scat.symbol

The identity of the atom specie(s) representing this atom type.
See [\_atom\_type.symbol](#_atom_type.symbol) for further details.

### <a name="_atom_type_scat.versus_stol_list"></a>\_atom\_type\_scat.versus\_stol\_list

List of scattering factors as a function of sin theta on lambda.
List has the form [[&lt;stol value 1&gt; &lt;scatfac 1&gt;] [&lt;stol value 2&gt; &lt;scatfac 2&gt;] ....] in
increments of 0.01, increasing from 0.0.

Units: none

## <a name="REFINE"></a>REFINE

The CATEGORY of data items used to specify information about the
refinement of the structural model.

### <a name="_refine.special_details"></a>\_refine.special\_details

Details of the refinement not specified by other data items.

## <a name="REFINE_DIFF"></a>REFINE\_DIFF

The CATEGORY of data items which specify the electron density limits
in a difference Fourier map after the structure has been refined. The
rms value is with respect to the arithmetic mean density, and is derived
from summations over each grid point in the asymmetric unit of the cell.

### <a name="_refine_diff.density_max"></a>\_refine\_diff.density\_max

Maximum density value in a difference Fourier map.

### <a name="_refine_diff.density_max_su"></a>\_refine\_diff.density\_max\_su

Standard Uncertainty of the
Maximum density value in a difference Fourier map.

### <a name="_refine_diff.density_min"></a>\_refine\_diff.density\_min

Miniumum density value in a difference Fourier map.

### <a name="_refine_diff.density_min_su"></a>\_refine\_diff.density\_min\_su

Standard Uncertainty of the
Miniumum density value in a difference Fourier map.

### <a name="_refine_diff.density_rms"></a>\_refine\_diff.density\_rms

Root mean square density value in a difference Fourier map.
This value is measured with respect to the arithmetic mean
density and is derived from summations over each grid point
in the asymmetric unit of the cell. This quantity is useful
for assessing the significance of \*\_min and \*\_max values,
and also for defining suitable contour levels.

### <a name="_refine_diff.density_rms_su"></a>\_refine\_diff.density\_rms\_su

Standard Uncertainty of the
Root mean square density value in a difference Fourier map.

## <a name="REFINE_LS"></a>REFINE\_LS

The CATEGORY of data items used to specify information about the
refinement of the structural model.

### <a name="_refine_ls.abs_structure_details"></a>\_refine\_ls.abs\_structure\_details

Details on the absolute structure and how it was determined.

### <a name="_refine_ls.abs_structure_Flack"></a>\_refine\_ls.abs\_structure\_Flack

The measure of absolute structure as defined by Flack (1983).
For centrosymmetric structures, the only permitted value, if the
data name is present, is &#39;inapplicable&#39;, represented by &#39;.&#39; .
For noncentrosymmetric structures, the value must lie in the
99.97% Gaussian confidence interval  -3u =&lt; x =&lt; 1 + 3u and a
standard uncertainty (e.s.d.) u must be supplied. The
\_enumeration.range of 0.0:1.0 is correctly interpreted as
meaning (0.0 - 3u) =&lt; x =&lt; (1.0 + 3u).
Ref: Flack, H. D. (1983). Acta Cryst. A39, 876-881.

Units: none

### <a name="_refine_ls.abs_structure_Flack_su"></a>\_refine\_ls.abs\_structure\_Flack\_su

Standard Uncertainty of the
The measure of absolute structure as defined by Flack (1983).

### <a name="_refine_ls.abs_structure_Rogers"></a>\_refine\_ls.abs\_structure\_Rogers

The measure of absolute structure as defined by Rogers (1981).
The value must lie in the 99.97% Gaussian confidence interval
-1 -3u =&lt; \h =&lt; 1 + 3u and a standard uncertainty (e.s.d.) u must
be supplied. The \_enumeration.range of -1.0:1.0 is correctly
interpreted as meaning (-1.0 - 3u) =&lt; \h =&lt; (1.0 + 3u).
Ref: Rogers, D. (1981). Acta Cryst. A37, 734-741.

Units: none

### <a name="_refine_ls.abs_structure_Rogers_su"></a>\_refine\_ls.abs\_structure\_Rogers\_su

Standard Uncertainty of the
The measure of absolute structure as defined by Rogers (1981).

### <a name="_refine_ls.d_res_high"></a>\_refine\_ls.d\_res\_high

Highest resolution for the reflections used in refinement.
This corresponds to the smallest interpanar d value.

Units: angstroms

### <a name="_refine_ls.d_res_low"></a>\_refine\_ls.d\_res\_low

Lowest resolution for the reflections used in refinement.
This corresponds to the largest interpanar d value.

Units: angstroms

### <a name="_refine_ls.extinction_coef"></a>\_refine\_ls.extinction\_coef

The extinction coefficient used to calculate the correction
factor applied to the structure-factor data. The nature of the
extinction coefficient is given in the definitions of
[\_refine\_ls.extinction\_expression](#_refine_ls.extinction_expression) and [\_refine\_ls.extinction\_method](#_refine_ls.extinction_method).
For the &#39;Zachariasen&#39; method it is the r\* value; for the
&#39;Becker-Coppens type 1 isotropic&#39; method it is the &#39;g&#39; value.
For &#39;Becker-Coppens type 2 isotropic&#39; corrections it is
the &#39;rho&#39; value. Note that the magnitude of these values is
usually of the order of 10000.
Ref:  Becker, P. J. &amp; Coppens, P. (1974). Acta Cryst. A30,
      129-147, 148-153.
      Zachariasen, W. H. (1967). Acta Cryst. 23, 558-564.
      Larson, A. C. (1967). Acta Cryst. 23, 664-665.

Units: none

Examples:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>
3472(52)
  </td><td>Zachariasen coefficient r* = 0.347(5)e+04
  </td></tr>
</table>
### <a name="_refine_ls.extinction_coef_su"></a>\_refine\_ls.extinction\_coef\_su

Standard Uncertainty of the extinction coefficient

Units: none

### <a name="_refine_ls.extinction_expression"></a>\_refine\_ls.extinction\_expression

Description of or reference to the extinction-correction equation
used to apply the data item  [\_refine\_ls.extinction\_coef](#_refine_ls.extinction_coef). This
information should be sufficient to reproduce the extinction-
correction factors applied to the structure factors.

Examples:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>
Larson approach
  </td><td>Larson, A. C. (1970). &quot;Crystallographic Computing&quot;, edited by
        F. R. Ahmed. Eq. (22) p. 292.  Copenhagen: Munksgaard.
  </td></tr>
</table>
### <a name="_refine_ls.extinction_method"></a>\_refine\_ls.extinction\_method

Description of the extinction correction method applied with the
data item [\_refine\_ls.extinction\_coef](#_refine_ls.extinction_coef). This description should
include information about the correction method, either &#39;Becker-
Coppens&#39; or &#39;Zachariasen&#39;. The latter is sometimes referred to as
the &#39;Larson&#39; method even though it employs Zachariasen&#39;s formula.

The Becker-Coppens procedure is referred to as &#39;type 1&#39; when
correcting secondary extinction dominated by the mosaic spread;
as &#39;type 2&#39; when secondary extinction is dominated by particle
size and includes a primary extinction component; and as &#39;mixed&#39;
when there are types 1 and 2.
 
For the Becker-Coppens method it is also necessary to set the
mosaic distribution as either &#39;Gaussian&#39; or &#39;Lorentzian&#39;; and the
nature of the extinction as &#39;isotropic&#39; or &#39;anisotropic&#39;. Note
that if either the &#39;mixed&#39; or &#39;anisotropic&#39; corrections are applied
the multiple coefficients cannot be contained in the
[\_refine\_ls.extinction\_coef](#_refine_ls.extinction_coef) and must be listed in [\_refine.special\_details](#_refine.special_details).

Ref:  Becker, P. J. &amp; Coppens, P. (1974). Acta Cryst. A30, 129-153.
      Zachariasen, W. H. (1967). Acta Cryst. 23, 558-564.
      Larson, A. C. (1967). Acta Cryst. 23, 664-665.

### <a name="_refine_ls.F_calc_details"></a>\_refine\_ls.F\_calc\_details

Details concerning the evaluation of the structure factors
using the expression given in [\_refine\_ls.F\_calc\_formula](#_refine_ls.F_calc_formula).

### <a name="_refine_ls.F_calc_formula"></a>\_refine\_ls.F\_calc\_formula

Analytical expression used to calculate the structure factors.

### <a name="_refine_ls.F_calc_precision"></a>\_refine\_ls.F\_calc\_precision

Estimate of the precision resulting from the numerical
approximations made during the evaluation of the structure
factors using the expression [\_refine\_ls.F\_calc\_formula](#_refine_ls.F_calc_formula)
following the method outlined in [\_refine\_ls.F\_calc\_details](#_refine_ls.F_calc_details).

### <a name="_refine_ls.goodness_of_fit_all"></a>\_refine\_ls.goodness\_of\_fit\_all

Least-squares goodness-of-fit parameter S for all reflections after
the final cycle of refinement. Ideally, account should be taken of
parameters restrained in the least squares.
 
         {  sum { w [ Y(meas) - Y(calc) ]^2^ }  }^1/2^
     S = { ------------------------------------ }
         {            Nref - Nparam             }
 
     Y(meas) = the measured coefficients
               (see [\_refine\_ls.structure\_factor\_coef](#_refine_ls.structure_factor_coef))
     Y(calc) = the calculated coefficients
               (see [\_refine\_ls.structure\_factor\_coef](#_refine_ls.structure_factor_coef))
     w       = the least-squares reflection weight
               [1/(u^2^)]
     u       = standard uncertainty
     Nref   = the number of reflections used in the refinement
     Nparam = the number of refined parameters
     and the sum is taken over the specified reflections

Units: none

### <a name="_refine_ls.goodness_of_fit_all_su"></a>\_refine\_ls.goodness\_of\_fit\_all\_su

Standard Uncertainty of the Least-squares goodness-of-fit
parameter S for all reflections after the final cycle of refinement.

Units: none

### <a name="_refine_ls.goodness_of_fit_gt"></a>\_refine\_ls.goodness\_of\_fit\_gt

Least-squares goodness-of-fit parameter S for significantly
intense reflections, (i.e. &#39;observed&#39; reflections with values
greater-than the threshold set in [\_reflns.threshold\_expression](#_reflns.threshold_expression)),
after the final cycle. Ideally, account should be taken of
parameters restrained in the least-squares refinement.
 
         {  sum { w [ Y(meas\_gt) - Y(calc) ]^2^ }  }^1/2^
     S = { --------------------------------------- }
         {           Nref - Nparam                 }
 
     Y(meas\_gt)  = the &#39;observed&#39; coefficients
               (see [\_refine\_ls.structure\_factor\_coef](#_refine_ls.structure_factor_coef))
     Y(calc)     = the calculated coefficients
               (see [\_refine\_ls.structure\_factor\_coef](#_refine_ls.structure_factor_coef))
     w       = the least-squares reflection weight
               [1/(u^2^)]
     u       = standard uncertainty
     Nref   = the number of reflections used in the refinement
     Nparam = the number of refined parameters
     and the sum is taken over the specified reflections

Units: none

### <a name="_refine_ls.goodness_of_fit_gt_su"></a>\_refine\_ls.goodness\_of\_fit\_gt\_su

Standard Uncertainty of the Least-squares goodness-of-fit
parameter S for gt reflections after the final cycle of refinement.

Units: none

### <a name="_refine_ls.goodness_of_fit_ref"></a>\_refine\_ls.goodness\_of\_fit\_ref

Least-squares goodness-of-fit parameter S for those reflections
included in the final cycle of refinement. Account should be
taken of restrained parameters.
 
         {  sum { w [ Y(meas) - Y(calc) ]^2^ }  }^1/2^
     S = { ------------------------------------ }
         {            Nref - Nparam             }
 
     Y(meas) = the measured coefficients
               (see [\_refine\_ls.structure\_factor\_coef](#_refine_ls.structure_factor_coef))
     Y(calc) = the calculated coefficients
               (see [\_refine\_ls.structure\_factor\_coef](#_refine_ls.structure_factor_coef))
     w       = the least-squares reflection weight
               [1/(u^2^)]
     u       = standard uncertainty
     Nref   = the number of reflections used in the refinement
     Nparam = the number of refined parameters
     and the sum is taken over the specified reflections

Units: none

### <a name="_refine_ls.hydrogen_treatment"></a>\_refine\_ls.hydrogen\_treatment

Code identifying how hydrogen atoms were treated in the refinement.

Values:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>refall</td><td>refined all H-atom parameters</td></tr>
  <tr><td>refxyz</td><td>refined H-atom coordinates only</td></tr>
  <tr><td>refU</td><td>refined H-atom Us only</td></tr>
  <tr><td>noref</td><td>no refinement of H-atom parameters</td></tr>
  <tr><td>constr</td><td>H-atom parameters constrained</td></tr>
  <tr><td>hetero</td><td>H-atom parameters constrained for H on C, all
               H-atom parameters refined for H on heteroatoms</td></tr>
  <tr><td>heteroxyz</td><td>H-atom parameters constrained for H on C, refined
               H-atom coordinates only for H on heteroatoms</td></tr>
  <tr><td>heteroU</td><td>H-atom parameters constrained for H on C, refined
               H-atom U&#39;s only for H on heteroatoms</td></tr>
  <tr><td>heteronoref</td><td>H-atom parameters constrained for H on C, no
               refinement of H-atom parameters for H on heteroatoms</td></tr>
  <tr><td>hetero-mixed</td><td>H-atom parameters constrained for H on C and some
               heteroatoms, all H-atom parameters refined
               for H on remaining heteroatoms</td></tr>
  <tr><td>heteroxyz-mixed</td><td>H-atom parameters constrained for H on C and some
               heteroatoms, refined H-atom coordinates only
               for H on remaining heteroatoms</td></tr>
  <tr><td>heteroU-mixed</td><td>H-atom parameters constrained for H on C and some
               heteroatoms, refined H-atom U&#39;s only for H on
               remaining heteroatoms</td></tr>
  <tr><td>heteronoref-mixed</td><td>H-atom parameters constrained for H on C and some
               heteroatoms, no refinement of H-atom parameters
               for H on remaining heteroatoms</td></tr>
  <tr><td>mixed</td><td>some constrained, some independent</td></tr>
  <tr><td>undef</td><td>H-atom parameters not defined</td></tr>
</table>
### <a name="_refine_ls.matrix_type"></a>\_refine\_ls.matrix\_type

Code identifying the matrix type used for least-squares derivatives.

Values:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>full</td><td>full</td></tr>
  <tr><td>fullcycle</td><td>full with fixed elements per cycle</td></tr>
  <tr><td>atomblock</td><td>block diagonal per atom</td></tr>
  <tr><td>userblock</td><td>user-defined blocks</td></tr>
  <tr><td>diagonal</td><td>diagonal elements only</td></tr>
  <tr><td>sparse</td><td>selected elements only</td></tr>
</table>
### <a name="_refine_ls.number_constraints"></a>\_refine\_ls.number\_constraints

Number of constrained (non-refined or dependent) parameters
in the least-squares process. These may be due to symmetry or any
other constraint process (e.g. rigid-body refinement). See also
[\_atom\_site.constraints](#_atom_site.constraints) and [\_atom\_site.refinement\_flags](#_atom_site.refinement_flags). A general
description of constraints may appear in [\_refine.special\_details](#_refine.special_details).

### <a name="_refine_ls.number_parameters"></a>\_refine\_ls.number\_parameters

Number of parameters refined in the least-squares process. If
possible this number should include the restrained parameters.
The restrained parameters are distinct from the constrained
parameters (where one or more parameters are linearly dependent
on the refined value of another).  Least-squares restraints
often depend on geometry or energy considerations and this
makes their direct contribution to this number, and to the
goodness-of-fit calculation, difficult to assess.

### <a name="_refine_ls.number_reflns"></a>\_refine\_ls.number\_reflns

Number of unique reflections used in the least-squares refinement.

### <a name="_refine_ls.number_reflns_gt"></a>\_refine\_ls.number\_reflns\_gt

The number of reflections that satisfy the resolution limits
established by [\_refine\_ls.d\_res\_high](#_refine_ls.d_res_high) and [\_refine\_ls.d\_res\_low](#_refine_ls.d_res_low)
and the observation limit established by
\_reflns.observed\_criterion.

### <a name="_refine_ls.number_restraints"></a>\_refine\_ls.number\_restraints

Number of restrained parameters in the least-squares refinement. These
parameters do not directly dependent on another refined parameter. Often
restrained parameters involve geometry or energy dependencies. See also
[\_atom\_site.constraints](#_atom_site.constraints) and [\_atom\_site.refinement\_flags](#_atom_site.refinement_flags). A description
of refinement constraints may appear in [\_refine.special\_details](#_refine.special_details).

### <a name="_refine_ls.R_factor_all"></a>\_refine\_ls.R\_factor\_all

Residual factor for all reflections satisfying the resolution limits
specified by [\_refine\_ls.d\_res\_high](#_refine_ls.d_res_high) and [\_refine\_ls.d\_res\_low](#_refine_ls.d_res_low). This is
the conventional R factor. See also wR factor definitions.
 
              sum | F(meas) - F(calc) |
          R = ------------------------
                    sum | F(meas) |
 
          F(meas) = the measured structure-factor amplitudes
          F(calc) = the calculated structure-factor amplitudes
          and the sum is taken over the specified reflections

Units: none

### <a name="_refine_ls.R_factor_gt"></a>\_refine\_ls.R\_factor\_gt

Residual factor for the reflections judged significantly intense
(see [\_reflns.number\_gt](#_reflns.number_gt) and [\_reflns.threshold\_expression](#_reflns.threshold_expression)) and included
in the refinement. The reflections also satisfy the resolution limits
specified by [\_refine\_ls.d\_res\_high](#_refine_ls.d_res_high) and [\_refine\_ls.d\_res\_low](#_refine_ls.d_res_low). This is
the conventional R factor.
 
              sum | F(meas\_gt) - F(calc) |
          R = -----------------------------
                    sum | F(meas\_gt) |
 
          F(meas\_gt) = the &#39;observed&#39; structure-factor amplitudes
          F(calc)    = the calculated structure-factor amplitudes
          and the sum is taken over the specified reflections

Units: none

### <a name="_refine_ls.R_Fsqd_factor"></a>\_refine\_ls.R\_Fsqd\_factor

Residual factor R(Fsqd), calculated on the squared amplitudes of the
measured and calculated structure factors, for significantly intense
reflections (satisfying [\_reflns.threshold\_expression](#_reflns.threshold_expression)) and included in
the refinement. The reflections also satisfy the resolution limits
specified by [\_refine\_ls.d\_res\_high](#_refine_ls.d_res_high) and [\_refine\_ls.d\_res\_low](#_refine_ls.d_res_low).
 
                     sum | F(meas\_gt)^2^ - F(calc)^2^ |
          R(Fsqd) = ------------------------------------
                             sum F(meas\_gt)^2^
 
          F(meas\_gt)^2^ = squares of the &#39;observed&#39; structure-factor
          F(calc)^2^    = squares of the calculated structure-factor
          and the sum is taken over the specified reflections

Units: none

### <a name="_refine_ls.R_I_factor"></a>\_refine\_ls.R\_I\_factor

Residual factor R(I) for significantly intense reflections (satisfying
[\_reflns.threshold\_expression](#_reflns.threshold_expression)) and included in the refinement. This is
most often calculated in Rietveld refinements of powder data, where it
is referred to as R~B~ or R~Bragg~.
 
                  sum | I(meas\_gt) - I(calc) |
          R(I) =  -----------------------------
                         sum | I(meas\_gt) |
 
          I(meas\_gt) = the net &#39;observed&#39; intensities
          I(calc)    = the net calculated intensities
          and the sum is taken over the specified reflections

Units: none

### <a name="_refine_ls.restrained_S_all"></a>\_refine\_ls.restrained\_S\_all

Least-squares goodness-of-fit parameter S&#39; for all reflections after
the final cycle of least squares. This parameter explicitly includes
the restraints applied in the least-squares process. See also
[\_refine\_ls.goodness\_of\_fit\_all](#_refine_ls.goodness_of_fit_all) definition.
 
       {sum { w [ Y(meas) - Y(calc) ]^2^ }                  }^1/2^
       {         + sum~r~ { w~r~ [ P(calc) - P(targ) ]^2^ } }
  S&#39; = { -------------------------------------------------- }
       {            N~ref~ + N~restr~ - N~param~            }
 
          Y(meas)  = the measured coefficients
                     (see [\_refine\_ls.structure\_factor\_coef](#_refine_ls.structure_factor_coef))
          Y(calc)  = the calculated coefficients
                     (see [\_refine\_ls.structure\_factor\_coef](#_refine_ls.structure_factor_coef))
          w        = the least-squares reflection weight
                     [1/square of standard uncertainty (e.s.d.)]
          P(calc)  = the calculated restraint values
          P(targ)  = the target restraint values
          w~r~     = the restraint weight
 
          N~ref~   = the number of reflections used in the refinement
                   (see [\_refine\_ls.number\_reflns](#_refine_ls.number_reflns))
          N~restr~ = the number of restraints
                   (see [\_refine\_ls.number\_restraints](#_refine_ls.number_restraints))
          N~param~ = the number of refined parameters
                   (see [\_refine\_ls.number\_parameters](#_refine_ls.number_parameters))
 
          sum     is taken over the specified reflections
          sum~r~  is taken over the restraints

Units: none

### <a name="_refine_ls.restrained_S_gt"></a>\_refine\_ls.restrained\_S\_gt

Least-squares goodness-of-fit parameter S&#39; for significantly intense
reflections (satisfying [\_reflns.threshold\_expression](#_reflns.threshold_expression)) after the final
cycle of least squares. This parameter explicitly includes the restraints
applied. The expression for S&#39; is given in [\_refine\_ls.restrained\_S\_all](#_refine_ls.restrained_S_all).
 
       {sum { w [ Y(meas\_gt) - Y(calc) ]^2^ }               }^1/2^
       {         + sum~r~ { w~r~ [ P(calc) - P(targ) ]^2^ } }
  S&#39; = { -------------------------------------------------- }
       {            N~ref~ + N~restr~ - N~param~            }
 
          Y(meas\_gt) = the &#39;observed&#39; coefficients
                     (see [\_refine\_ls.structure\_factor\_coef](#_refine_ls.structure_factor_coef))
          Y(calc)    = the calculated coefficients
                     (see [\_refine\_ls.structure\_factor\_coef](#_refine_ls.structure_factor_coef))
          w        = the least-squares reflection weight
                     [1/square of standard uncertainty (e.s.d.)]
          P(calc)  = the calculated restraint values
          P(targ)  = the target restraint values
          w~r~     = the restraint weight
 
          N~ref~   = the number of reflections used in the refinement
                   (see [\_refine\_ls.number\_reflns](#_refine_ls.number_reflns))
          N~restr~ = the number of restraints
                   (see [\_refine\_ls.number\_restraints](#_refine_ls.number_restraints))
          N~param~ = the number of refined parameters
                   (see [\_refine\_ls.number\_parameters](#_refine_ls.number_parameters))
 
          sum     is taken over the specified reflections
          sum~r~  is taken over the restraints

Units: none

### <a name="_refine_ls.shift_over_su_max"></a>\_refine\_ls.shift\_over\_su\_max

The largest ratio of the final least-squares parameter shift
to the final standard uncertainty (s.u., formerly described
as estimated standard deviation, e.s.d.).

Units: none

### <a name="_refine_ls.shift_over_su_max_lt"></a>\_refine\_ls.shift\_over\_su\_max\_lt

Upper limit for the largest ratio of the final l-s parameter
shift divided by the final standard uncertainty. This item is
used when the largest value of the shift divided by the final
standard uncertainty is too small to measure.

Units: none

### <a name="_refine_ls.shift_over_su_mean"></a>\_refine\_ls.shift\_over\_su\_mean

The average ratio of the final least-squares parameter shift
to the final standard uncertainty (s.u., formerly described
as estimated standard deviation, e.s.d.).

Units: none

### <a name="_refine_ls.shift_over_su_mean_lt"></a>\_refine\_ls.shift\_over\_su\_mean\_lt

Upper limit for the average ratio of the final l-s parameter
shift divided by the final standard uncertainty. This item is
used when the average value of the shift divided by the final
standard uncertainty is too small to measure.

Units: none

### <a name="_refine_ls.structure_factor_coef"></a>\_refine\_ls.structure\_factor\_coef

Structure-factor coefficient used in the least-squares process.

Values:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>F</td><td>structure factor magnitude</td></tr>
  <tr><td>Fsqd</td><td>structure factor squared</td></tr>
  <tr><td>Inet</td><td>net intensity</td></tr>
</table>
### <a name="_refine_ls.weighting_details"></a>\_refine\_ls.weighting\_details

Description of special aspects of the weighting scheme used in the
least-squares refinement. Used to describe the weighting when the
value of [\_refine\_ls.weighting\_scheme](#_refine_ls.weighting_scheme) is specified as &#39;calc&#39;.

### <a name="_refine_ls.weighting_scheme"></a>\_refine\_ls.weighting\_scheme

General description of the weighting scheme used in the least-squares.
An enumerated code should be contained in this description.

Values:

<table>
  <tr><th>Value</th><th>Description</th></tr>
  <tr><td>sigma</td><td>based on measured s.u.&#39;s</td></tr>
  <tr><td>unit</td><td>unit or no weights applied</td></tr>
  <tr><td>calc</td><td>calculated weights applied</td></tr>
</table>
### <a name="_refine_ls.wR_factor_all"></a>\_refine\_ls.wR\_factor\_all

Weighted residual factors for all reflections satisfying the resolution
limits specified by [\_refine\_ls.d\_res\_high](#_refine_ls.d_res_high) and [\_refine\_ls.d\_res\_low](#_refine_ls.d_res_low).
See also the [\_refine\_ls.R\_factor\_all](#_refine_ls.R_factor_all) definition.
 
       ( sum w [ Y(meas) - Y(calc) ]^2^ )^1/2^
  wR = ( ------------------------------ )
       (         sum w Y(meas)^2^       )
 
  Y(meas) = the measured   amplitude [\_refine\_ls.structure\_factor\_coef](#_refine_ls.structure_factor_coef)
  Y(calc) = the calculated amplitude [\_refine\_ls.structure\_factor\_coef](#_refine_ls.structure_factor_coef)
  w       = the least-squares weight
  and the sum is taken over the specified reflections

Units: none

### <a name="_refine_ls.wR_factor_gt"></a>\_refine\_ls.wR\_factor\_gt

Weighted residual factors for significantly intense reflections
(satisfying [\_reflns.threshold\_expression](#_reflns.threshold_expression)) included in the refinement.
The reflections must also satisfy the resolution limits established by
[\_refine\_ls.d\_res\_high](#_refine_ls.d_res_high) and [\_refine\_ls.d\_res\_low](#_refine_ls.d_res_low).
 
       ( sum w [ Y(meas\_gt) - Y(calc) ]^2^  )^1/2^
  wR = ( ---------------------------------- )
       (         sum w Y(meas\_gt)^2^        )
 
Y(meas\_gt) = the &#39;observed&#39; amplitude [\_refine\_ls.structure\_factor\_coef](#_refine_ls.structure_factor_coef)
Y(calc)    = the calculated amplitude [\_refine\_ls.structure\_factor\_coef](#_refine_ls.structure_factor_coef)
  w        = the least-squares weight
  and the sum is taken over the specified reflections

Units: none

### <a name="_refine_ls.wR_factor_ref"></a>\_refine\_ls.wR\_factor\_ref

Weighted residual factors for reflections included in the refinement
which satisfy the limits specified by [\_refine\_ls.d\_res\_high](#_refine_ls.d_res_high) and
[\_refine\_ls.d\_res\_low](#_refine_ls.d_res_low).
 
       ( sum w [ Y(meas) - Y(calc) ]^2^ )^1/2^
  wR = ( ------------------------------ )
       (         sum w Y(meas)^2^       )
 
  Y(meas) = the measured   amplitude [\_refine\_ls.structure\_factor\_coef](#_refine_ls.structure_factor_coef)
  Y(calc) = the calculated amplitude [\_refine\_ls.structure\_factor\_coef](#_refine_ls.structure_factor_coef)
  w       = the least-squares weight
  and the sum is taken over the specified reflections

Units: none

## <a name="REFINE_LS_CLASS"></a>REFINE\_LS\_CLASS

The CATEGORY of data items used to specify information about the
refinement of the structural model.

### <a name="_refine_ls_class.code"></a>\_refine\_ls\_class.code

Code identifying a certain reflection class.

### <a name="_refine_ls_class.d_res_high"></a>\_refine\_ls\_class.d\_res\_high

Highest resolution for the reflections in this class.
This corresponds to the smallest interpanar d value.

Units: angstroms

### <a name="_refine_ls_class.d_res_low"></a>\_refine\_ls\_class.d\_res\_low

Lowest resolution for the reflections in this class.
This corresponds to the largest interpanar d value.

Units: angstroms

### <a name="_refine_ls_class.R_factor_all"></a>\_refine\_ls\_class.R\_factor\_all

Residual factor for reflections in this class included in the
refinement.  See [\_refine\_ls.R\_factor\_all](#_refine_ls.R_factor_all) definition for details.

Units: none

### <a name="_refine_ls_class.R_factor_gt"></a>\_refine\_ls\_class.R\_factor\_gt

Residual factor for the reflections in this class judged
significantly intense (see [\_reflns.threshold\_expression](#_reflns.threshold_expression)) and
included in refinement. See [\_refine\_ls.R\_factor\_gt](#_refine_ls.R_factor_gt) for details.

Units: none

### <a name="_refine_ls_class.R_Fsqd_factor"></a>\_refine\_ls\_class.R\_Fsqd\_factor

Residual factor R(F^2^) for reflections in this class judged
significantly intense (see [\_reflns.threshold\_expression](#_reflns.threshold_expression)) and
included in refinement. See [\_refine\_ls.R\_Fsqd\_factor](#_refine_ls.R_Fsqd_factor) for details.

Units: none

### <a name="_refine_ls_class.R_I_factor"></a>\_refine\_ls\_class.R\_I\_factor

Residual factor R(I) for reflections in this class judged
significantly intense (see [\_reflns.threshold\_expression](#_reflns.threshold_expression)) and
included in refinement. See [\_refine\_ls.R\_I\_factor](#_refine_ls.R_I_factor) for details.

Units: none

### <a name="_refine_ls_class.wR_factor_all"></a>\_refine\_ls\_class.wR\_factor\_all

Weight residual for all reflections in this class judged
significantly intense (see [\_reflns.threshold\_expression](#_reflns.threshold_expression)) and
included in refinement. See [\_refine\_ls.wR\_factor\_all](#_refine_ls.wR_factor_all) for details.

Units: none

