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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>
</CENTER>
<HR>
<H3>fix freeze command
</H3>
<H3>fix freeze/cuda command
</H3>
<P><B>Syntax:</B>
</P>
<PRE>fix ID group-ID freeze
</PRE>
<UL><LI>ID, group-ID are documented in <A HREF = "fix.html">fix</A> command
<LI>freeze = style name of this fix command
</UL>
<P><B>Examples:</B>
</P>
<PRE>fix 2 bottom freeze
</PRE>
<P><B>Description:</B>
</P>
<P>Zero out the force and torque on a granular particle. This is useful
for preventing certain particles from moving in a simulation. The
<A HREF = "pair_gran.html">granular pair styles</A> also detect if this fix has been
defined and compute interactions between frozen and non-frozen
particles appropriately, as if the frozen particle has infinite mass.
A similar functionality for normal (point) particles can be obtained
using <A HREF = "fix_setforce.html">fix setforce</A>.
</P>
<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
<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.
</P>
<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.
</P>
<P>You can specify the accelerated styles explicitly in your input script
by including their suffix, or you can use the <A HREF = "Section_start.html#start_7">-suffix command-line
switch</A> when you invoke LAMMPS, or you can
use the <A HREF = "suffix.html">suffix</A> command in your input script.
</P>
<P>See <A HREF = "Section_accelerate.html">Section_accelerate</A> of the manual for
more instructions on how to use the accelerated styles effectively.
</P>
<HR>
<P><B>Restart, fix_modify, output, run start/stop, minimize info:</B>
</P>
<P>No information about this fix is written to <A HREF = "restart.html">binary restart
files</A>. None of the <A HREF = "fix_modify.html">fix_modify</A> options
are relevant to this fix.
</P>
<P>This fix computes a global 3-vector of forces, which can be accessed
by various <A HREF = "Section_howto.html#howto_15">output commands</A>. This is the
total force on the group of atoms before the forces on individual
atoms are changed by the fix. The vector values calculated by this
fix are "extensive".
</P>
<P>No parameter of this fix can be used with the <I>start/stop</I> keywords of
the <A HREF = "run.html">run</A> command. This fix is not invoked during <A HREF = "minimize.html">energy
minimization</A>.
</P>
<P><B>Restrictions:</B>
</P>
<P>This fix is part of the GRANULAR package. It is 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.
</P>
<P>There can only be a single freeze fix defined. This is because other
the <A HREF = "pair_gran.html">granular pair styles</A> treat frozen particles
differently and need to be able to reference a single group to which
this fix is applied.
</P>
<P><B>Related commands:</B>
</P>
<P><A HREF = "atom_style.html">atom_style sphere</A>, <A HREF = "fix_setforce.html">fix setforce</A>
</P>
<P><B>Default:</B> none
</P>
</HTML>
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