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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 wall/lj93 command
</H3>
<P><B>Syntax:</B>
</P>
<PRE>fix ID group-ID wall/lj93 style coord epsilon sigma cutoff
</PRE>
<UL><LI>ID, group-ID are documented in <A HREF = "fix.html">fix</A> command
<LI>wall/lj93 = style name of this fix command
<LI>style = <I>xlo</I> or <I>xhi</I> or <I>ylo</I> or <I>yhi</I> or <I>zlo</I> or <I>zhi</I>
<LI>coord = position of wall
<LI>epsilon = Lennard-Jones epsilon for wall-particle interaction
<LI>sigma = Lennard-Jones sigma for wall-particle interaction
<LI>cutoff = distance from wall at which wall-particle interaction is cut off
</UL>
<P><B>Examples:</B>
</P>
<PRE>fix wallhi all wall/lj93 xhi 10.0 1.0 1.0 1.12
</PRE>
<P><B>Description:</B>
</P>
<P>Bound the simulation domain with a Lennard-Jones wall that encloses
the atoms. The energy E of a wall-particle interactions is given by
the 9-3 potential
</P>
<CENTER><IMG SRC = "Eqs/fix_wall_lj93.jpg">
</CENTER>
<P>where <I>r</I> is the distance from the particle to the wall <I>coord</I>, and
epsilon and sigma are the usual LJ parameters. Rc is the cutoff value
specified in the command. This interaction is derived by integrating
over a 3d half-lattice of Lennard-Jones 12-6 particles.
</P>
<P>This fix supports the <A HREF = "fix_modify.html">fix_modify</A> options for
<I>thermo</I> and <I>energy</I>. The former will print the contribution the fix
makes to the energy of the system when thermodynamics is printed,
where the energy of each particle comes from the integrated form of
the equation above. The latter will add this contribution to the
total potential energy (PotEng).
</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. If you
want that energy to be included in the total potential energy of the
system (the quantity being minimized), you must enable the
<A HREF = "fix_modify.html">fix_modify</A> <I>energy</I> option for this fix.
</P>
<P><B>Restrictions:</B> none
</P>
<P><B>Related commands:</B>
</P>
<P><A HREF = "fix_wall_reflect.html">fix wall/reflect</A> command
</P>
<P><B>Default:</B> none
</P>
</HTML>
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