2006-09-22 00:22:34 +08:00
|
|
|
<HTML>
|
|
|
|
|
<CENTER><A HREF = "http://lammps.sandia.gov">LAMMPS WWW Site</A> - <A HREF = "Manual.html">LAMMPS Documentation</A> - <A HREF = "Section_commands.html#comm">LAMMPS Commands</A>
|
|
|
|
|
</CENTER>
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
<HR>
|
|
|
|
|
|
2010-09-02 06:32:30 +08:00
|
|
|
<H3>fix temp/rescale command
|
2006-09-22 00:22:34 +08:00
|
|
|
</H3>
|
2011-06-09 05:46:03 +08:00
|
|
|
<H3>fix temp/rescale/cuda command
|
|
|
|
|
</H3>
|
|
|
|
|
<H3>fix temp/rescale/limit/cuda command
|
|
|
|
|
</H3>
|
2006-09-22 00:22:34 +08:00
|
|
|
<P><B>Syntax:</B>
|
|
|
|
|
</P>
|
2010-09-02 06:32:30 +08:00
|
|
|
<PRE>fix ID group-ID temp/rescale N Tstart Tstop window fraction
|
2006-09-22 00:22:34 +08:00
|
|
|
</PRE>
|
2012-05-24 21:31:42 +08:00
|
|
|
<UL><LI>ID, group-ID are documented in <A HREF = "fix.html">fix</A> command
|
|
|
|
|
|
|
|
|
|
<LI>temp/rescale = style name of this fix command
|
|
|
|
|
|
|
|
|
|
<LI>N = perform rescaling every N steps
|
|
|
|
|
|
|
|
|
|
<LI>Tstart,Tstop = desired temperature at start/end of run (temperature units)
|
|
|
|
|
|
|
|
|
|
<PRE> Tstart can be a variable (see below)
|
|
|
|
|
</PRE>
|
|
|
|
|
<LI>window = only rescale if temperature is outside this window (temperature units)
|
|
|
|
|
|
2008-03-12 01:15:19 +08:00
|
|
|
<LI>fraction = rescale to target temperature by this fraction
|
2006-09-22 00:22:34 +08:00
|
|
|
</UL>
|
|
|
|
|
<P><B>Examples:</B>
|
|
|
|
|
</P>
|
2010-09-02 06:32:30 +08:00
|
|
|
<PRE>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
|
|
|
|
|
fix 3 boundary temp/rescale 1 1.0 1.5 0.05 1.0
|
2006-09-22 00:22:34 +08:00
|
|
|
</PRE>
|
|
|
|
|
<P><B>Description:</B>
|
|
|
|
|
</P>
|
|
|
|
|
<P>Reset the temperature of a group of atoms by explicitly rescaling
|
|
|
|
|
their velocities.
|
|
|
|
|
</P>
|
2010-09-02 06:32:30 +08:00
|
|
|
<P>The rescaling is applied to only the translational degrees of freedom
|
2013-02-01 03:46:51 +08:00
|
|
|
for the particles, which is an important consideration if finite-size
|
|
|
|
|
particles which have rotational degrees of freedom are being
|
|
|
|
|
thermostatted with this fix. The translational degrees of freedom can
|
|
|
|
|
also have a bias velocity removed from them before thermostatting
|
|
|
|
|
takes place; see the description below.
|
2008-03-20 06:51:12 +08:00
|
|
|
</P>
|
2006-09-22 00:22:34 +08:00
|
|
|
<P>Rescaling is performed every N timesteps. The target temperature is a
|
|
|
|
|
ramped value between the <I>Tstart</I> and <I>Tstop</I> temperatures at the
|
2007-06-26 08:03:39 +08:00
|
|
|
beginning and end of the run.
|
2006-09-22 00:22:34 +08:00
|
|
|
</P>
|
2012-05-24 21:31:42 +08:00
|
|
|
<P><I>Tstart</I> can be specified as an equal-style <A HREF = "variable.html">variable</A>.
|
|
|
|
|
In this case, the <I>Tstop</I> setting is ignored. If the value is a
|
|
|
|
|
variable, it should be specified as v_name, where name is the variable
|
|
|
|
|
name. In this case, the variable will be evaluated each timestep, and
|
|
|
|
|
its value used to determine the target temperature.
|
|
|
|
|
</P>
|
|
|
|
|
<P>Equal-style variables can specify formulas with various mathematical
|
|
|
|
|
functions, and include <A HREF = "thermo_style.html">thermo_style</A> command
|
|
|
|
|
keywords for the simulation box parameters and timestep and elapsed
|
|
|
|
|
time. Thus it is easy to specify a time-dependent temperature.
|
|
|
|
|
</P>
|
2006-09-22 00:22:34 +08:00
|
|
|
<P>Rescaling is only performed if the difference between the current and
|
|
|
|
|
desired temperatures is greater than the <I>window</I> value. The amount
|
|
|
|
|
of rescaling that is applied is a <I>fraction</I> (from 0.0 to 1.0) of the
|
|
|
|
|
difference between the actual and desired temperature. E.g. if
|
|
|
|
|
<I>fraction</I> = 1.0, the temperature is reset to exactly the desired
|
|
|
|
|
value.
|
|
|
|
|
</P>
|
2010-09-02 06:32:30 +08:00
|
|
|
<P>IMPORTANT NOTE: Unlike the <A HREF = "fix_nh.html">fix nvt</A> command which
|
2008-03-12 01:15:19 +08:00
|
|
|
performs Nose/Hoover thermostatting AND time integration, this fix
|
|
|
|
|
does NOT perform time integration. It only modifies velocities to
|
|
|
|
|
effect thermostatting. Thus you must use a separate time integration
|
2010-09-02 06:32:30 +08:00
|
|
|
fix, like <A HREF = "fix_nve.html">fix nve</A> to actually update the positions of
|
|
|
|
|
atoms using the modified velocities. Likewise, this fix should not
|
2008-03-12 01:15:19 +08:00
|
|
|
normally be used on atoms that also have their temperature controlled
|
2010-09-02 06:32:30 +08:00
|
|
|
by another fix - e.g. by <A HREF = "fix_nh.html">fix nvt</A> or <A HREF = "fix_langevin.html">fix
|
|
|
|
|
langevin</A> commands.
|
2006-09-22 00:22:34 +08:00
|
|
|
</P>
|
2011-08-26 01:01:01 +08:00
|
|
|
<P>See <A HREF = "Section_howto.html#howto_16">this howto section</A> of the manual for
|
|
|
|
|
a discussion of different ways to compute temperature and perform
|
2008-04-05 05:15:50 +08:00
|
|
|
thermostatting.
|
|
|
|
|
</P>
|
2007-02-10 05:37:30 +08:00
|
|
|
<P>This fix computes a temperature each timestep. To do this, the fix
|
2008-03-12 01:15:19 +08:00
|
|
|
creates its own compute of style "temp", as if one of this command had
|
|
|
|
|
been issued:
|
2007-02-10 05:37:30 +08:00
|
|
|
</P>
|
2010-09-02 06:32:30 +08:00
|
|
|
<PRE>compute fix-ID_temp group-ID temp
|
2007-02-10 05:37:30 +08:00
|
|
|
</PRE>
|
2010-09-02 06:32:30 +08:00
|
|
|
<P>See the <A HREF = "compute_temp.html">compute temp</A> for details. Note that the
|
|
|
|
|
ID of the new compute is the fix-ID + underscore + "temp", and the
|
2008-03-12 01:15:19 +08:00
|
|
|
group for the new compute is the same as the fix group.
|
2007-02-10 05:37:30 +08:00
|
|
|
</P>
|
|
|
|
|
<P>Note that this is NOT the compute used by thermodynamic output (see
|
|
|
|
|
the <A HREF = "thermo_style.html">thermo_style</A> command) with ID = <I>thermo_temp</I>.
|
|
|
|
|
This means you can change the attributes of this fix's temperature
|
|
|
|
|
(e.g. its degrees-of-freedom) via the
|
|
|
|
|
<A HREF = "compute_modify.html">compute_modify</A> command or print this temperature
|
2008-03-01 09:13:20 +08:00
|
|
|
during thermodynamic output via the <A HREF = "thermo_style.html">thermo_style
|
2007-02-10 05:37:30 +08:00
|
|
|
custom</A> command using the appropriate compute-ID.
|
|
|
|
|
It also means that changing attributes of <I>thermo_temp</I> will have no
|
2007-06-26 08:03:39 +08:00
|
|
|
effect on this fix.
|
|
|
|
|
</P>
|
2008-03-12 01:15:19 +08:00
|
|
|
<P>Like other fixes that perform thermostatting, this fix can be used
|
|
|
|
|
with <A HREF = "compute.html">compute commands</A> that calculate a temperature
|
|
|
|
|
after removing a "bias" from the atom velocities. E.g. removing the
|
|
|
|
|
center-of-mass velocity from a group of atoms or only calculating
|
|
|
|
|
temperature on the x-component of velocity or only calculating
|
|
|
|
|
temperature for atoms in a geometric region. This is not done by
|
|
|
|
|
default, but only if the <A HREF = "fix_modify.html">fix_modify</A> command is used
|
|
|
|
|
to assign a temperature compute to this fix that includes such a bias
|
|
|
|
|
term. See the doc pages for individual <A HREF = "compute.html">compute
|
|
|
|
|
commands</A> to determine which ones include a bias. In
|
|
|
|
|
this case, the thermostat works in the following manner: the current
|
|
|
|
|
temperature is calculated taking the bias into account, bias is
|
|
|
|
|
removed from each atom, thermostatting is performed on the remaining
|
|
|
|
|
thermal degrees of freedom, and the bias is added back in.
|
|
|
|
|
</P>
|
2011-06-09 05:46:03 +08:00
|
|
|
<HR>
|
|
|
|
|
|
|
|
|
|
<P>Styles with a <I>cuda</I> suffix are functionally the same as the
|
|
|
|
|
corresponding style without the suffix. They have been optimized to
|
|
|
|
|
run faster, depending on your available hardware, as discussed in
|
2011-12-14 04:35:35 +08:00
|
|
|
<A HREF = "Section_accelerate.html">Section_accelerate</A> of the manual. The
|
|
|
|
|
accelerated styles take the same arguments and should produce the same
|
|
|
|
|
results, except for round-off and precision issues.
|
2011-06-09 05:46:03 +08:00
|
|
|
</P>
|
2011-08-27 02:53:00 +08:00
|
|
|
<P>These accelerated styles are part of the USER-CUDA package. They are
|
|
|
|
|
only enabled if LAMMPS was built with that package. See the <A HREF = "Section_start.html#start_3">Making
|
|
|
|
|
LAMMPS</A> section for more info.
|
2011-06-09 05:46:03 +08:00
|
|
|
</P>
|
|
|
|
|
<P>You can specify the accelerated styles explicitly in your input script
|
2012-01-28 07:39:14 +08:00
|
|
|
by including their suffix, or you can use the <A HREF = "Section_start.html#start_7">-suffix command-line
|
2011-08-26 00:46:23 +08:00
|
|
|
switch</A> when you invoke LAMMPS, or you can
|
|
|
|
|
use the <A HREF = "suffix.html">suffix</A> command in your input script.
|
2011-06-09 05:46:03 +08:00
|
|
|
</P>
|
2011-12-14 04:35:35 +08:00
|
|
|
<P>See <A HREF = "Section_accelerate.html">Section_accelerate</A> of the manual for
|
|
|
|
|
more instructions on how to use the accelerated styles effectively.
|
2011-06-09 05:46:03 +08:00
|
|
|
</P>
|
|
|
|
|
<HR>
|
|
|
|
|
|
2007-10-11 06:28:11 +08:00
|
|
|
<P><B>Restart, fix_modify, output, run start/stop, minimize info:</B>
|
2007-06-26 08:03:39 +08:00
|
|
|
</P>
|
|
|
|
|
<P>No information about this fix is written to <A HREF = "restart.html">binary restart
|
|
|
|
|
files</A>.
|
|
|
|
|
</P>
|
|
|
|
|
<P>The <A HREF = "fix_modify.html">fix_modify</A> <I>temp</I> option is supported by this
|
2008-03-12 01:15:19 +08:00
|
|
|
fix. You can use it to assign a temperature <A HREF = "compute.html">compute</A>
|
|
|
|
|
you have defined to this fix which will be used in its thermostatting
|
|
|
|
|
procedure, as described above. For consistency, the group used by
|
|
|
|
|
this fix and by the compute should be the same.
|
2007-06-26 08:03:39 +08:00
|
|
|
</P>
|
|
|
|
|
<P>The <A HREF = "fix_modify.html">fix_modify</A> <I>energy</I> option is supported by this
|
|
|
|
|
fix to add the energy change implied by a velocity rescaling to the
|
|
|
|
|
system's potential energy as part of <A HREF = "thermo_style.html">thermodynamic
|
2009-05-12 21:33:47 +08:00
|
|
|
output</A>.
|
2007-10-10 02:24:42 +08:00
|
|
|
</P>
|
2010-04-03 00:51:06 +08:00
|
|
|
<P>This fix computes a global scalar which can be accessed by various
|
2011-08-26 01:01:01 +08:00
|
|
|
<A HREF = "Section_howto.html#howto_15">output commands</A>. The scalar is the
|
2010-04-03 00:51:06 +08:00
|
|
|
cummulative energy change due to this fix. The scalar value
|
|
|
|
|
calculated by this fix is "extensive".
|
2007-06-26 08:03:39 +08:00
|
|
|
</P>
|
|
|
|
|
<P>This fix can ramp its target temperature over multiple runs, using the
|
|
|
|
|
<I>start</I> and <I>stop</I> keywords of the <A HREF = "run.html">run</A> command. See the
|
|
|
|
|
<A HREF = "run.html">run</A> command for details of how to do this.
|
|
|
|
|
</P>
|
|
|
|
|
<P>This fix is not invoked during <A HREF = "minimize.html">energy minimization</A>.
|
2006-09-22 00:22:34 +08:00
|
|
|
</P>
|
2010-09-02 06:32:30 +08:00
|
|
|
<P><B>Restrictions:</B> none
|
2006-09-22 00:22:34 +08:00
|
|
|
</P>
|
|
|
|
|
<P><B>Related commands:</B>
|
|
|
|
|
</P>
|
2010-09-02 06:32:30 +08:00
|
|
|
<P><A HREF = "fix_langevin.html">fix langevin</A>, <A HREF = "fix_nh.html">fix nvt</A>,
|
2006-09-22 00:22:34 +08:00
|
|
|
<A HREF = "fix_modify.html">fix_modify</A>
|
|
|
|
|
</P>
|
|
|
|
|
<P><B>Default:</B> none
|
|
|
|
|
</P>
|
|
|
|
|
</HTML>
|
