forked from lijiext/lammps
99 lines
3.9 KiB
Plaintext
99 lines
3.9 KiB
Plaintext
"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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fix temp/rescale command :h3
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[Syntax:]
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fix ID group-ID temp/rescale N Tstart Tstop window fraction keyword values ... :pre
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ID, group-ID are documented in "fix"_fix.html command :ulb,l
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temp/rescale = style name of this fix command :l
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N = perform rescaling every N steps :l
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Tstart,Tstop = desired temperature at start/end of run (temperature units) :l
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window = only rescale if temperature is outside this window (temperature units) :l
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fraction = rescale to target temperature by this fraction :l
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zero or more keyword/value pairs may be appended to the args :l
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keyword = {region}
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{region} values = region-ID
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region-ID = ID of region to apply rescaling to :pre
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:ule
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[Examples:]
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fix 3 flow temp/rescale 100 1.0 1.1 0.02 0.5
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fix 3 boundary temp/rescale 1 1.0 1.5 0.05 1.0 region edge :pre
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[Description:]
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Reset the temperature of a group of atoms by explicitly rescaling
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their velocities.
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Rescaling is performed every N timesteps. The target temperature is a
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ramped value between the {Tstart} and {Tstop} temperatures at the
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beginning and end of the run. The "run"_run.html command documents
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how to make the ramping take place across multiple runs.
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Rescaling is only performed if the difference between the current and
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desired temperatures is greater than the {window} value. The amount
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of rescaling that is applied is a {fraction} (from 0.0 to 1.0) of the
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difference between the actual and desired temperature. E.g. if
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{fraction} = 1.0, the temperature is reset to exactly the desired
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value.
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The keyword {region} applies the fix only to atoms that are in the
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specified geometric region (and in the fix group). Since atoms can
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enter/leave a region, this test is performed each timestep.
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This fix computes a temperature each timestep. The fix creates its
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own method for computing T, as if it had been defined by one of these
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commands:
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temperature fix-ID group-ID full
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temperature fix-ID group-ID region region-ID :pre
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Which is used depends on whether a region was specified with the fix.
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See the "temperature"_temperature.html command for details. Note that
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this is NOT the temperature with ID = {default}. This means you can
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change the attributes of this fix's temperature (e.g. its
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degrees-of-freedom) via the "temp_modify"_temp_modify.html command or
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print the temperature with thermodyanmic output via the "thermo_style
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custom"_thermo_style.html command using the appropriate temp-ID =
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fix-ID. It also means that changing attributes of the default
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temperature will have no effect on this fix. Alternatively, you can
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directly assign a new temperature to the fix via the
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"fix_modify"_fix_modify.html command. For consistency, if using the
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keyword {region}, the temperature you assign should also be of style
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{region}.
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A temp/rescale fix does not update the coordinates of its atoms. It
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is normally used with a fix of style {nve} that does that. A
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temp/rescale fix should not normally be used on atoms that also have
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their temperature controlled by another fix - e.g. a
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"nvt"_fix_nvt.html or "langevin"_fix_langevin.html fix.
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This fix supports the "fix_modify"_fix_modify.html options for
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{thermo} and {energy}. The former will print the contribution the fix
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makes to the energy of the system when thermodynamics is printed. The
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latter will add this contribution to the total potential energy
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(PotEng) so that energy conservation can be monitored. Note that the
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energy value printed by thermo is not cummulative energy, but energy
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added in the most recent rescaling. Also note that because this fix
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is invoked every N steps and thermo may be printed every M steps, that
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unless M is a multiple of N, the energy info printed by thermo will
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not be for the current timestep.
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[Restrictions:] none
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[Related commands:]
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"fix langevin"_fix_langevin.html, "fix nvt"_fix_nvt.html,
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"fix_modify"_fix_modify.html
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[Default:] none
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