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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>
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<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>
<P>The forces due to this fix are also imposed during an energy
minimization, invoked by the <A HREF = "minimize.html">minimize</A> command.
</P>
<P>The total force on the group of atoms before it is reset is stored by
the fix and its components can be accessed during thermodynamic
print-out by using f_ID[N] where ID = he fix-ID and N = 1,2,3. See
the <A HREF = "thermo_style.html">thermo_style custom</A> command for details. Note
that the fix stores the total force on the group of atoms, but the
printed value may be normalized by the total number of atoms in the
simulation depending on the <A HREF = "thermo_modify.html">thermo_modify norm</A>
option you are using.
</P>
<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>
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