2007-02-10 05:40:32 +08:00
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"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c
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:link(lws,http://lammps.sandia.gov)
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:link(ld,Manual.html)
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:link(lc,Section_commands.html#comm)
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:line
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compute temp/region command :h3
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[Syntax:]
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compute ID group-ID temp/region region-ID :pre
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ID, group-ID are documented in "compute"_compute.html command
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temp/region = style name of this compute command
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region-ID = ID of region to use for choosing atoms :ul
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[Examples:]
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temperature mine flow region boundary :pre
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[Description:]
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Define a computation that calculates the temperature of a group of
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atoms in a geometric region. This can be useful for thermostatting
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one portion of the simulation box. E.g. a McDLT simulation where one
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side is cooled, and the other side is heated. A compute of this style
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can be used by any command that computes a temperature,
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e.g. "thermo_modify"_thermo_modify.html, "fix
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temp/rescale"_fix_temp_rescale.html, etc.
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Note that a {region}-style temperature can be used to thermostat with
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"fix temp/rescale"_fix_temp_rescale.html or "fix
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langevin"_fix_langevin.html, but should probably not be used with
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2007-04-20 07:25:27 +08:00
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Nose/Hoover style fixes ("fix nvt"_fix_nvt.html, "fix
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2007-02-10 05:40:32 +08:00
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npt"_fix_npt.html, or "fix nph"_fix_nph.html), if the
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degrees-of-freedom included in the computed T varies with time.
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The temperature is calculated by the formula KE = dim/2 N k T, where
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KE = total kinetic energy of the group of atoms (sum of 1/2 m v^2),
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dim = 2 or 3 = dimensionality of the simulation, N = number of atoms
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in both the group and region, k = Boltzmann constant, and T =
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temperature.
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A 6-component kinetic energy tensor is also calculated by this compute
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for use in the computation of a pressure tensor. The formula for the
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components of the tensor is the same as the above formula, except that
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v^2 is replaced by vx * vy for the xy component, etc.
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The number of atoms contributing to the temperature is compute each
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time the temperature is evaluated since it is assumed atoms can
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enter/leave the region. Thus there is no need to use the {dynamic}
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option of the "compute_modify"_compute_modify.html command for this
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compute style.
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Unlike other compute styles that calculate temperature, this compute
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does NOT currently subtract out degrees-of-freedom due to fixes that
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constrain molecular motion, such as "fix shake"_fix_shake.html and
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"fix rigid"_fix_rigid.html. If needed the subtracted
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degrees-of-freedom can be altered using the {extra} option of the
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"compute_modify"_compute_modify.html command.
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[Restrictions:] none
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[Related commands:]
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"compute temp"_compute_temp.html, "compute
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pressure"_compute_pressure.html
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[Default:] none
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