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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 oneway command
</H3>
<P><B>Syntax:</B>
</P>
<PRE>fix ID group-ID N oneway region-ID direction
</PRE>
<UL><LI>ID, group-ID are documented in <A HREF = "fix.html">fix</A> command
<LI>oneway = style name of this fix command
<LI>N = apply this fix every this many timesteps
<LI>region-ID = ID of region where fix is active
<LI>direction = <I>x</I> or <I>-x</I> or <I>y</I> or <I>-y</I> or <I>z</I> or <I>-z</I> = coordinate and direction of the oneway constraint
</UL>
<P><B>Examples:</B>
</P>
<PRE>fix ions 10 oneway semi -x
fix all 1 oneway left -z
fix all 1 oneway right z
</PRE>
<P><B>Description:</B>
</P>
<P>Enforce that particles in the group and in a given region can only
move in one direction. This is done by reversing a particle's
velocity component, if it has the wrong sign in the specified
dimension. The effect is that the particle moves in one direction
only.
</P>
<P>This can be used, for example, as a simple model of a semi-permeable
membrane, or as an implementation of Maxwell's demon.
</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. No global or per-atom quantities are stored
by this fix for access by various <A HREF = "Section_howto.html#howto_15">output
commands</A>. 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> 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>
<HR>
</HTML>
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