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<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>
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<H3>fix temp/rescale command
</H3>
<P><B>Syntax:</B>
</P>
<PRE>fix ID group-ID temp/rescale N Tstart Tstop window fraction keyword values ...
</PRE>
<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)
<LI>window = only rescale if temperature is outside this window (temperature units)
<LI>fraction = rescale to target temperature by this fraction
<LI>zero or more keyword/value pairs may be appended to the args
<LI>keyword = <I>region</I>
</UL>
<PRE> <I>region</I> values = region-ID of region to apply rescaling to
</PRE>
<P><B>Examples:</B>
</P>
<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 region edge
</PRE>
<P><B>Description:</B>
</P>
<P>Reset the temperature of a group of atoms by explicitly rescaling
their velocities.
</P>
<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
beginning and end of the run. The <A HREF = "run.html">run</A> command documents
how to make the ramping take place across multiple runs.
</P>
<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>
<P>The keyword <I>region</I> 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.
</P>
<P>A temp/rescale fix does not update the coordinates of its atoms. It
is normally used with a fix of style <I>nve</I> 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
<A HREF = "fix_nvt.html">nvt</A> or <A HREF = "fix_langevin.html">langevin</A> fix.
</P>
<P>This fix computes a temperature each timestep. To do this, the fix
creates its own compute of style "temp" or "temp/region", as if one of
these commands had been issued:
</P>
<PRE>compute fix-ID_temp group-ID temp
compute fix-ID_temp group-ID temp/region region-ID
</PRE>
<P>Which is used depends on whether a region was specified with the fix.
See the <A HREF = "compute_temp.html">compute temp</A> and <A HREF = "compute_temp_region.html">compute
temp/region</A> commands for details. Note that
the ID of the new compute is the fix-ID with underscore + "temp"
appended and the group for the new compute is the same as the fix
group.
</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
during thermodyanmic output via the <A HREF = "thermo_style.html">thermo_style
custom</A> command using the appropriate compute-ID.
It also means that changing attributes of <I>thermo_temp</I> will have no
effect on this fix. Alternatively, you can directly assign a new
compute (for calculating temeperature) that you have defined to this
fix via the <A HREF = "fix_modify.html">fix_modify</A> command. For consistency, if
using the keyword <I>region</I>, the compute you assign should also be of
style <I>temp/region</I>.
</P>
<P>This fix makes a contribution to the potential energy of the system
that can be included in thermodynamic output of potential energy using
the <A HREF = "fix_modify.html">fix_modify energy</A> option. The contribution can
also be printed by itself via the keyword <I>f_fix-ID</I> in the
<A HREF = "thermo_style.html">thermo_style custom</A> command. Note that because
this fix is invoked every N steps and thermodynamic info may be
printed every M steps, that unless M is a multiple of N, the energy
info accessed will not be for the current timestep.
</P>
<P><B>Restrictions:</B> none
</P>
<P><B>Related commands:</B>
</P>
<P><A HREF = "fix_langevin.html">fix langevin</A>, <A HREF = "fix_nvt.html">fix nvt</A>,
<A HREF = "fix_modify.html">fix_modify</A>
</P>
<P><B>Default:</B> none
</P>
</HTML>
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