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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>pair_style born/coul/long/cs command
</H3>
<H3>pair_style buck/coul/long/cs command
</H3>
<P><B>Syntax:</B>
</P>
<PRE>pair_style style args
</PRE>
<UL><LI>style = <I>born/coul/long/cs</I> or <I>buck/coul/long/cs</I>
<LI>args = list of arguments for a particular style
</UL>
<PRE> <I>born/coul/long/cs</I> args = cutoff (cutoff2)
cutoff = global cutoff for non-Coulombic (and Coulombic if only 1 arg) (distance units)
cutoff2 = global cutoff for Coulombic (optional) (distance units)
<I>buck/coul/long/cs</I> args = cutoff (cutoff2)
cutoff = global cutoff for Buckingham (and Coulombic if only 1 arg) (distance units)
cutoff2 = global cutoff for Coulombic (optional) (distance units)
</PRE>
<P><B>Examples:</B>
</P>
<PRE>pair_style born/coul/long/cs 10.0 8.0
pair_coeff 1 1 6.08 0.317 2.340 24.18 11.51
</PRE>
<PRE>pair_style buck/coul/long/cs 10.0
pair_style buck/coul/long/cs 10.0 8.0
pair_coeff * * 100.0 1.5 200.0
pair_coeff 1 1 100.0 1.5 200.0 9.0
</PRE>
<P><B>Description:</B>
</P>
<P>These pair styles are designed to be used with the adiabatic
core/shell model of <A HREF = "#MitchellFinchham">(Mitchell and Finchham)</A>. See
<A HREF = "Section_howto.html#howto_25">Section_howto 25</A> of the manual for an
overview of the model as implemented in LAMMPS.
</P>
<P>These pair styles are identical to the <A HREF = "pair_born.html">pair_style
born/coul/long</A> and <A HREF = "pair_buck.html">pair_style
buck/coul/long</A> styles, except they correctly treat the
special case where the distance between two charged core and shell
atoms in the same core/shell pair approach r = 0.0. This needs
special treatment when a long-range solver for Coulombic interactions
is also used, i.e. via the <A HREF = "kspace_style.html">kspace_style</A> command.
</P>
<P>More specifically, the short-range Coulomb interaction between a core
and its shell should be turned off using the
<A HREF = "special_bonds.html">special_bonds</A> command by setting the 1-2 weight
to 0.0, which works because the core and shell atoms are bonded to
each other. This induces a long-range correction approximation which
fails at small distances (~< 10e-8). Therefore, the Coulomb term which
is used to calculate the correction factor is extended by a minimal
distance (r_min = 1.0-6) when the interaction between a core/shell
pair is treated, as follows
</P>
<CENTER><IMG SRC = "Eqs/pair_cs.jpg">
</CENTER>
<P>where C is an energy-conversion constant, Qi and Qj are the charges on
the core and shell, epsilon is the dielectric constant and r_min is the
minimal distance.
</P>
<P><B>Restrictions:</B>
</P>
<P>These pair styles are part of the CORESHELL package. They are only
enabled if LAMMPS was built with that package. See the <A HREF = "Section_start.html#start_3">Making
LAMMPS</A> section for more info.
</P>
<P><B>Related commands:</B>
</P>
<P><A HREF = "pair_coeff.html">pair_coeff</A>, <A HREF = "pair_born.html">pair_style born</A>,
<A HREF = "pair_buck.html">pair_style buck</A>
</P>
<P><B>Default:</B> none
</P>
<HR>
<A NAME = "MitchellFinchham"></A>
<P><B>(Mitchell and Finchham)</B> Mitchell, Finchham, J Phys Condensed Matter,
5, 1031-1038 (1993).
</P>
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