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>
|
|
|
|
|
|
|
|
|
|
<H3>fix setforce command
|
|
|
|
|
</H3>
|
|
|
|
|
<P><B>Syntax:</B>
|
|
|
|
|
</P>
|
|
|
|
|
<PRE>fix ID group-ID setforce fx fy fz
|
|
|
|
|
</PRE>
|
|
|
|
|
<UL><LI>ID, group-ID are documented in <A HREF = "fix.html">fix</A> command
|
|
|
|
|
<LI>setforce = style name of this fix command
|
|
|
|
|
<LI>fx,fy,fz = force component values
|
|
|
|
|
</UL>
|
|
|
|
|
<P><B>Examples:</B>
|
|
|
|
|
</P>
|
|
|
|
|
<PRE>fix freeze indenter setforce 0.0 0.0 0.0
|
|
|
|
|
fix 2 edge setforce NULL 0.0 0.0
|
|
|
|
|
</PRE>
|
|
|
|
|
<P><B>Description:</B>
|
|
|
|
|
</P>
|
|
|
|
|
<P>Set each component of force on each atom in the group to the specified
|
|
|
|
|
values fx,fy,fz. This erases all previously computed forces on the
|
|
|
|
|
atom, though additional fixes could add new forces. This command can
|
|
|
|
|
be used to freeze certain atoms in the simulation by zeroing their
|
|
|
|
|
force, assuming their initial velocity zero.
|
|
|
|
|
</P>
|
|
|
|
|
<P>Any of the fx,fy,fz values can be specified as NULL which means do not
|
|
|
|
|
alter the force component in that dimension.
|
|
|
|
|
</P>
|
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>. None of the <A HREF = "fix_modify.html">fix_modify</A> options
|
|
|
|
|
are relevant to this fix.
|
|
|
|
|
</P>
|
2007-10-10 02:24:42 +08:00
|
|
|
<P>This fix computes a 3-vector of forces, which can be accessed by
|
|
|
|
|
various <A HREF = "Section_howto.html#4_15">output commands</A>. This is the total
|
|
|
|
|
force on the group of atoms before the forces on individual atoms are
|
2008-01-03 03:25:15 +08:00
|
|
|
reset by the fix. The vector values calculated by this fix are
|
|
|
|
|
"extensive", meaning they scale with the number of atoms in the
|
|
|
|
|
simulation.
|
2007-06-26 08:03:39 +08:00
|
|
|
</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.
|
|
|
|
|
</P>
|
|
|
|
|
<P>The forces due to this fix are imposed during an energy minimization,
|
|
|
|
|
invoked by the <A HREF = "minimize.html">minimize</A> command.
|
2007-03-23 00:35:32 +08:00
|
|
|
</P>
|
2006-09-22 00:22:34 +08:00
|
|
|
<P><B>Restrictions:</B> none
|
|
|
|
|
</P>
|
|
|
|
|
<P><B>Related commands:</B>
|
|
|
|
|
</P>
|
|
|
|
|
<P><A HREF = "fix_addforce.html">fix addforce</A>, <A HREF = "fix_aveforce.html">fix aveforce</A>
|
|
|
|
|
</P>
|
|
|
|
|
<P><B>Default:</B> none
|
|
|
|
|
</P>
|
|
|
|
|
</HTML>
|
