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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>neighbor command
</H3>
<P><B>Syntax:</B>
</P>
<PRE>neighbor skin style
</PRE>
<UL><LI>skin = extra distance beyond force cutoff (distance units)
<LI>style = <I>bin</I> or <I>nsq</I>
</UL>
<P><B>Examples:</B>
</P>
<PRE>neighbor 0.3 bin
neighbor 2.0 nsq
</PRE>
<P><B>Description: </B>
</P>
<P>This command sets parameters that affect the building of the pairwise
neighbor list. All atom pairs within a cutoff distance equal to the
their force cutoff plus the <I>skin</I> distance are stored in the list.
Typically, the larger the skin distance, the less often neighbor lists
need to be built, but more pairs must be checked for possible force
interactions every timestep.
</P>
<P>The <I>style</I> value chooses what algorithm is used to build the list.
<I>Binning</I> is an operation that scales linearly with N, the number of
atoms on a processor. It is almost always faster than the <I>nsq</I> style
which scales as N^2. For unsolvated small molecules in a non-periodic
box, the <I>nsq</I> choice can sometimes be faster. Either style should
give the same answers.
</P>
<P>The default values for <I>skin</I> and <I>style</I> depend on the choice of
units for the simulation.
</P>
<P>The <A HREF = "neigh_modify.html">neigh_modify</A> command has additional options
that control how often neighbor lists are built and which pairs are
stored in the list.
</P>
<P>When a run is finished, counts of the number of neighbors stored in
the pairwise list and the number of times neighbor lists were built
are printed to the screen and log file. See <A HREF = "Section_start.html#2_5">this
section</A> for details.
</P>
<P><B>Restrictions:</B> none
</P>
<P><B>Related commands:</B>
</P>
<P><A HREF = "neigh_modify.html">neigh_modify</A>, <A HREF = "units.html">units</A>
</P>
<P><B>Default:</B>
</P>
<PRE>0.3 bin for lj units
2.0 bin for real or metal units
</PRE>
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