.. index:: compute ke/atom/eff

compute ke/atom/eff command
===========================

Syntax
""""""

.. code-block:: LAMMPS

   compute ID group-ID ke/atom/eff

* ID, group-ID are documented in :doc:`compute <compute>` command
* ke/atom/eff = style name of this compute command

Examples
""""""""

.. code-block:: LAMMPS

   compute 1 all ke/atom/eff

Description
"""""""""""

Define a computation that calculates the per-atom translational
(nuclei and electrons) and radial kinetic energy (electron only) in a
group.  The particles are assumed to be nuclei and electrons modeled
with the :doc:`electronic force field <pair_eff>`.

The kinetic energy for each nucleus is computed as :math:`\frac{1}{2} m
v^2`, where *m* corresponds to the corresponding nuclear mass, and the
kinetic energy for each electron is computed as :math:`\frac{1}{2} (m_e
v^2 + \frac{3}{4} m_e s^2)`, where :math:`m_e` and *v* correspond to the mass
and translational velocity of each electron, and *s* to its radial
velocity, respectively.

There is a subtle difference between the quantity calculated by this
compute and the kinetic energy calculated by the *ke* or *etotal*
keyword used in thermodynamic output, as specified by the
:doc:`thermo_style <thermo_style>` command. For this compute, kinetic
energy is "translational" plus electronic "radial" kinetic energy,
calculated by the simple formula above. For thermodynamic output, the
*ke* keyword infers kinetic energy from the temperature of the system
with :math:`\frac{1}{2} k_B T` of energy for each (nuclear-only) degree
of freedom in eFF.

.. note::

   The temperature in eFF should be monitored via the :doc:`compute temp/eff <compute_temp_eff>` command, which can be printed with
   thermodynamic output by using the :doc:`thermo_modify <thermo_modify>`
   command, as shown in the following example:

.. code-block:: LAMMPS

   compute         effTemp all temp/eff
   thermo_style    custom step etotal pe ke temp press
   thermo_modify   temp effTemp

The value of the kinetic energy will be 0.0 for atoms (nuclei or
electrons) not in the specified compute group.

Output info
"""""""""""

This compute calculates a scalar quantity for each atom, which can be
accessed by any command that uses per-atom computes as input.  See the
:doc:`Howto output <Howto_output>` page for an overview of LAMMPS
output options.

The per-atom vector values will be in energy :doc:`units <units>`.

Restrictions
""""""""""""

This compute is part of the EFF package.  It is only enabled if
LAMMPS was built with that package.  See the :doc:`Build package <Build_package>` page for more info.

Related commands
""""""""""""""""

:doc:`dump custom <dump>`

Default
"""""""

none
