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