forked from lijiext/lammps
56 lines
1.7 KiB
HTML
56 lines
1.7 KiB
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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>
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</CENTER>
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<HR>
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<H3>fix aveforce command
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</H3>
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<P><B>Syntax:</B>
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</P>
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<PRE>fix ID group-ID aveforce fx fy fz
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</PRE>
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<UL><LI>ID, group-ID are documented in <A HREF = "fix.html">fix</A> command
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<LI>aveforce = style name of this fix command
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<LI>fx,fy,fz = force component values (force units)
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</UL>
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<P><B>Examples:</B>
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</P>
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<PRE>fix pressdown topwall aveforce 0.0 -1.0 0.0
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fix 2 bottomwall aveforce NULL -1.0 0.0
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</PRE>
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<P><B>Description:</B>
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</P>
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<P>Apply an additional external force to a group of atoms in such a way
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that every atom experiences the same force. This is useful for
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pushing on wall or boundary atoms so that the structure of the wall
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does not change over time.
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</P>
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<P>The existing force is averaged for the group of atoms, component by
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component. The actual force on each atom is then set to the average
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value plus the component specified in this command. This means each
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atom in the group receives the same force.
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</P>
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<P>If any of the arguments is specified as NULL then the forces in that
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dimension are not changed. Note that this is not the same as
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specifying a 0.0 value, since that sets all forces to the same average
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value without adding in any additional force.
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</P>
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<P>The forces due to this fix are also imposed during an energy
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minimization, invoked by the <A HREF = "minimize.html">minimize</A> command.
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</P>
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<P><B>Restrictions:</B> none
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</P>
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<P><B>Related commands:</B>
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</P>
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<P><A HREF = "fix_setforce.html">fix setforce</A>, <A HREF = "fix_addforce.html">fix addforce</A>
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</P>
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<P><B>Default:</B> none
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</P>
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</HTML>
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