forked from lijiext/lammps
89 lines
2.6 KiB
Plaintext
89 lines
2.6 KiB
Plaintext
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.. index:: compute ke/atom/eff
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compute ke/atom/eff command
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===========================
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Syntax
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""""""
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.. parsed-literal::
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compute ID group-ID ke/atom/eff
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* ID, group-ID are documented in :doc:`compute <compute>` command
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* ke/atom/eff = style name of this compute command
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Examples
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""""""""
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.. parsed-literal::
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compute 1 all ke/atom/eff
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Description
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"""""""""""
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Define a computation that calculates the per-atom translational
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(nuclei and electrons) and radial kinetic energy (electron only) in a
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group. The particles are assumed to be nuclei and electrons modeled
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with the :doc:`electronic force field <pair_eff>`.
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The kinetic energy for each nucleus is computed as 1/2 m v^2, where m
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corresponds to the corresponding nuclear mass, and the kinetic energy
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for each electron is computed as 1/2 (me v^2 + 3/4 me s^2), where me
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and v correspond to the mass and translational velocity of each
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electron, and s to its radial velocity, respectively.
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There is a subtle difference between the quantity calculated by this
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compute and the kinetic energy calculated by the *ke* or *etotal*
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keyword used in thermodynamic output, as specified by the
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:doc:`thermo_style <thermo_style>` command. For this compute, kinetic
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energy is "translational" plus electronic "radial" kinetic energy,
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calculated by the simple formula above. For thermodynamic output, the
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*ke* keyword infers kinetic energy from the temperature of the system
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with 1/2 Kb T of energy for each (nuclear-only) degree of freedom in
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eFF.
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.. note::
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The temperature in eFF should be monitored via the :doc:`compute temp/eff <compute_temp_eff>` command, which can be printed with
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thermodynamic output by using the :doc:`thermo_modify <thermo_modify>`
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command, as shown in the following example:
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.. parsed-literal::
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compute effTemp all temp/eff
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thermo_style custom step etotal pe ke temp press
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thermo_modify temp effTemp
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The value of the kinetic energy will be 0.0 for atoms (nuclei or
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electrons) not in the specified compute group.
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**Output info:**
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This compute calculates a scalar quantity for each atom, which can be
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accessed by any command that uses per-atom computes as input. See
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:ref:`Section_howto 15 <howto_15>` for an overview of
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LAMMPS output options.
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The per-atom vector values will be in energy :doc:`units <units>`.
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Restrictions
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""""""""""""
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This compute is part of the USER-EFF package. It is only enabled if
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LAMMPS was built with that package. See the :ref:`Making LAMMPS <start_3>` section for more info.
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Related commands
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""""""""""""""""
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:doc:`dump custom <dump>`
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**Default:** none
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.. _lws: http://lammps.sandia.gov
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.. _ld: Manual.html
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.. _lc: Section_commands.html#comm
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