91 lines
2.8 KiB
ReStructuredText
91 lines
2.8 KiB
ReStructuredText
.. index:: compute temp/drude
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compute temp/drude command
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==========================
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Syntax
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""""""
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.. code-block:: LAMMPS
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compute ID group-ID temp/drude
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* ID, group-ID are documented in :doc:`compute <compute>` command
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* temp/drude = style name of this compute command
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Examples
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""""""""
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.. code-block:: LAMMPS
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compute TDRUDE all temp/drude
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Example input scripts available: :file:`examples/PACKAGES/drude`.
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Description
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"""""""""""
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Define a computation that calculates the temperatures of core--Drude
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pairs. This compute is designed to be used with the
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:doc:`thermalized Drude oscillator model <Howto_drude>`.
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Polarizable models in LAMMPS
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are described on the :doc:`Howto polarizable <Howto_polarizable>` doc page.
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Drude oscillators consist of a core particle and a Drude particle
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connected by a harmonic bond, and the relative motion of these Drude
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oscillators is usually maintained cold by a specific thermostat that
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acts on the relative motion of the core--Drude particle
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pairs. Therefore, because LAMMPS considers Drude particles as normal
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atoms in its default temperature compute (:doc:`compute temp <compute_temp>`
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command), the reduced temperature of the core--Drude particle pairs is not
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calculated correctly.
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By contrast, this compute calculates the temperature of the cores
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using center-of-mass velocities of the core--Drude pairs, and the
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reduced temperature of the Drude particles using the relative
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velocities of the Drude particles with respect to their cores.
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Non-polarizable atoms are considered as cores. Their velocities
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contribute to the temperature of the cores.
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Output info
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"""""""""""
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This compute calculates a global scalar (the temperature) and a global
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vector of length 6, which can be accessed by indices 1--6, whose components
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are
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1. temperature of the centers of mass (temperature units)
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2. temperature of the dipoles (temperature units)
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3. number of degrees of freedom of the centers of mass
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4. number of degrees of freedom of the dipoles
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5. kinetic energy of the centers of mass (energy units)
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6. kinetic energy of the dipoles (energy units)
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These values can be used by any command that uses global scalar or
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vector values from a compute as input. See the
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:doc:`Howto output <Howto_output>` page for an overview of LAMMPS output
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options.
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Both the scalar value and the first two values of the vector
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calculated by this compute are "intensive". The other four vector values
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are "extensive".
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Restrictions
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""""""""""""
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The number of degrees of freedom contributing to the temperature is
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assumed to be constant for the duration of the run unless the
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*fix_modify* command sets the option *dynamic yes*\ .
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Related commands
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""""""""""""""""
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:doc:`fix drude <fix_drude>`, :doc:`fix langevin/drude <fix_langevin_drude>`,
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:doc:`fix drude/transform <fix_drude_transform>`,
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:doc:`pair_style thole <pair_thole>`, :doc:`compute temp <compute_temp>`
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Default
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"""""""
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none
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