forked from lijiext/lammps
70 lines
1.9 KiB
Plaintext
70 lines
1.9 KiB
Plaintext
.. index:: compute ke
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compute ke 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
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* ID, group-ID are documented in :doc:`compute <compute>` command
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* ke = 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
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Description
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"""""""""""
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Define a computation that calculates the translational kinetic energy
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of a group of particles.
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The kinetic energy of each particle is computed as 1/2 m v^2, where m
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and v are the mass and velocity of the particle.
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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" kinetic energy, calculated by the simple
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formula above. For thermodynamic output, the *ke* keyword infers
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kinetic energy from the temperature of the system with 1/2 Kb T of
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energy for each degree of freedom. For the default temperature
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computation via the :doc:`compute temp <compute_temp>` command, these
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are the same. But different computes that calculate temperature can
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subtract out different non-thermal components of velocity and/or
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include different degrees of freedom (translational, rotational, etc).
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**Output info:**
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This compute calculates a global scalar (the summed KE). This value
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can be used by any command that uses a global scalar value from a
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compute as input. See :ref:`Section_howto 15 <howto_15>`
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for an overview of LAMMPS output options.
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The scalar value calculated by this compute is "extensive". The
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scalar value will be in energy :doc:`units <units>`.
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Restrictions
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""""""""""""
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none
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Related commands
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""""""""""""""""
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:doc:`compute erotate/sphere <compute_erotate_sphere>`
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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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