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fix_freeze.html
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Sun, Sep 8, 21:18
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rLAMMPS lammps
fix_freeze.html
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<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 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.
</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"
>
this section
</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_6"
>
-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"
>
this section
</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>
none
</P>
<P><A
HREF =
"atom_style.html"
>
atom_style sphere
</A>
</P>
<P><B>
Default:
</B>
none
</P>
</HTML>
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