Page Menu
Home
c4science
Search
Configure Global Search
Log In
Files
F102265163
fix_temp_rescale.html
No One
Temporary
Actions
Download File
Edit File
Delete File
View Transforms
Subscribe
Mute Notifications
Award Token
Subscribers
None
File Metadata
Details
File Info
Storage
Attached
Created
Tue, Feb 18, 21:59
Size
4 KB
Mime Type
text/html
Expires
Thu, Feb 20, 21:59 (2 d)
Engine
blob
Format
Raw Data
Handle
24316493
Attached To
rLAMMPS lammps
fix_temp_rescale.html
View Options
<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>
<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>
Event Timeline
Log In to Comment