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 wall/reflect command
|
|
|
|
|
</H3>
|
|
|
|
|
<P><B>Syntax:</B>
|
|
|
|
|
</P>
|
|
|
|
|
<PRE>fix ID group-ID wall/reflect keyword ...
|
|
|
|
|
</PRE>
|
|
|
|
|
<UL><LI>ID, group-ID are documented in <A HREF = "fix.html">fix</A> command
|
|
|
|
|
<LI>wall/reflect = style name of this fix command
|
2007-07-03 04:04:44 +08:00
|
|
|
<LI>one or more keyword/value pairs may be appended
|
2006-09-22 00:22:34 +08:00
|
|
|
<LI>keyword = <I>xlo</I> or <I>xhi</I> or <I>ylo</I> or <I>yhi</I> or <I>zlo</I> or <I>zhi</I>
|
|
|
|
|
</UL>
|
|
|
|
|
<P><B>Examples:</B>
|
|
|
|
|
</P>
|
|
|
|
|
<PRE>fix xwalls all wall/reflect xlo xhi
|
|
|
|
|
fix walls all wall/reflect xlo ylo zlo xhi yhi zhi
|
|
|
|
|
</PRE>
|
|
|
|
|
<P><B>Description:</B>
|
|
|
|
|
</P>
|
|
|
|
|
<P>Bound the simulation with one or more walls which reflect particles
|
2007-03-08 09:01:08 +08:00
|
|
|
when they attempt to move thru them.
|
2006-09-22 00:22:34 +08:00
|
|
|
</P>
|
|
|
|
|
<P>Reflection means that if an atom moves outside the box on a timestep
|
|
|
|
|
by a distance delta (e.g. due to <A HREF = "fix_nve.html">fix nve</A>), then it is
|
|
|
|
|
put back inside the box by the same delta and the sign of the
|
|
|
|
|
corresponding component of its velocity is flipped.
|
|
|
|
|
</P>
|
2008-05-14 05:49:52 +08:00
|
|
|
<P>When used in conjunction with <A HREF = "fix_nve.html">fix nve</A> and <A HREF = "run_style.html">run_style
|
|
|
|
|
verlet</A>, the resultant time-integration algorithm is
|
|
|
|
|
equivalent to the primitive splitting algorithm (PSA) described by
|
|
|
|
|
<A HREF = "#Bond">Bond</A>. Because each reflection event divides
|
|
|
|
|
the corresponding timestep asymmetrically, energy conservation is only
|
|
|
|
|
satisfied to O(dt), rather than to O(dt^2) as it would be for
|
|
|
|
|
velocity-Verlet integration without reflective walls.
|
|
|
|
|
</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
|
2007-10-11 06:28:11 +08:00
|
|
|
are relevant to this fix. No global scalar or vector or per-atom
|
|
|
|
|
quantities are stored by this fix for access by various <A HREF = "Section_howto.html#4_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>.
|
2007-06-26 08:03:39 +08:00
|
|
|
</P>
|
2007-03-08 09:01:08 +08:00
|
|
|
<P><B>Restrictions:</B>
|
|
|
|
|
</P>
|
|
|
|
|
<P>Any dimension (xyz) that has a reflecting wall must be non-periodic.
|
2006-09-22 00:22:34 +08:00
|
|
|
</P>
|
2007-03-09 23:20:25 +08:00
|
|
|
<P>A reflecting wall cannot be used with rigid bodies such as those
|
|
|
|
|
defined by a "fix rigid" command. This is because the wall/reflect
|
|
|
|
|
displaces atoms directly rather than exerts a force on them. For
|
|
|
|
|
rigid bodies, use a soft wall instead, such as <A HREF = "fix_wall_lj93.html">fix
|
|
|
|
|
wall/lj93</A>.
|
|
|
|
|
</P>
|
2006-09-22 00:22:34 +08:00
|
|
|
<P><B>Related commands:</B>
|
|
|
|
|
</P>
|
|
|
|
|
<P><A HREF = "fix_wall_lj93.html">fix wall/lj93</A> command
|
|
|
|
|
</P>
|
|
|
|
|
<P><B>Default:</B> none
|
|
|
|
|
</P>
|
2008-05-14 05:49:52 +08:00
|
|
|
<A NAME = "Bond"></A>
|
|
|
|
|
|
|
|
|
|
<P><B>(Bond)</B> Bond and Leimkuhler, SIAM J Sci Comput, 30, p 134 (2007).
|
|
|
|
|
</P>
|
2006-09-22 00:22:34 +08:00
|
|
|
</HTML>
|
