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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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<H3>fix evaporate command
</H3>
<P><B>Syntax:</B>
</P>
<PRE>fix ID group-ID evaporate N M region-ID seed
</PRE>
<UL><LI>ID, group-ID are documented in <A HREF = "fix.html">fix</A> command
<LI>evaporate = style name of this fix command
<LI>N = delete atoms every this many timesteps
<LI>M = number of atoms to delete each time
<LI>region-ID = ID of region within which to perform deletions
<LI>seed = random number seed to use for choosing atoms to delete
</UL>
<P><B>Examples:</B>
</P>
<PRE>fix 1 solvent evaporate 1000 10 surface 49892
</PRE>
<P><B>Description:</B>
</P>
<P>Remove M atoms from the simulation every N steps. This can be used,
for example, to model evaporation of solvent particles (i.e. drying)
of a system. Every N steps, the number of atoms in the fix group and
within the specifed region are counted. M of these are chosen at
random and deleted. If there are less than M eligible particles, then
all of them are deleted.
</P>
<P>Note that you cannot currently delete solvent molecules with this
command, only individual atoms. If you delete only one atom in a
molecule, an error will result.
</P>
<P>Note that neighbor lists are re-built on timesteps that atoms are
removed. Thus you should not remove atoms too frequently or you will
incur overhead due to the cost of building neighbor lists.
</P>
<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.
</P>
<P>This fix computes a global scalar, which can be accessed by various
<A HREF = "Section_howto.html#4_15">output commands</A>. The scalar is the
cummulative number of deleted atoms. The scalar value calculated by
this fix is "intensive".
</P>
<P>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_deposit.html">fix deposit</A>
</P>
<P><B>Default:</B> none
</P>
</HTML>
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