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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 sph/idealgas command
</H3>
<P><B>Syntax:</B>
</P>
<PRE>pair_style sph/idealgas
</PRE>
<P><B>Examples:</B>
</P>
<PRE>pair_style sph/idealgas
pair_coeff * * 1.0 2.4
</PRE>
<P><B>Description:</B>
</P>
<P>The sph/idealgas style computes pressure forces between particles
according to the ideal gas equation of state:
</P>
<CENTER><IMG SRC = "Eqs/pair_sph_ideal.jpg">
</CENTER>
<P>where gamma = 1.4 is the heat capacity ratio, rho is the local
density, and e is the internal energy per unit mass. This pair style
also computes Monaghan's artificial viscosity to prevent particles
from interpentrating <A HREF = "#Monoghan">(Monaghan)</A>.
</P>
<P>See <A HREF = "USER/sph/SPH_LAMMPS_userguide.pdf">this PDF guide</A> to using SPH in
LAMMPS.
</P>
<P>The following coefficients must be defined for each pair of atoms
types via the <A HREF = "pair_coeff.html">pair_coeff</A> command as in the examples
above.
</P>
<UL><LI>nu artificial viscosity (no units)
<LI>h kernel function cutoff (distance units)
</UL>
<HR>
<P><B>Mixing, shift, table, tail correction, restart, rRESPA info</B>:
</P>
<P>This style does not support mixing. Thus, coefficients for all
I,J pairs must be specified explicitly.
</P>
<P>This style does not support the <A HREF = "pair_modify.html">pair_modify</A>
shift, table, and tail options.
</P>
<P>This style does not write information to <A HREF = "restart.html">binary restart
files</A>. Thus, you need to re-specify the pair_style and
pair_coeff commands in an input script that reads a restart file.
</P>
<P>This style can only be used via the <I>pair</I> keyword of the <A HREF = "run_style.html">run_style
respa</A> command. It does not support the <I>inner</I>,
<I>middle</I>, <I>outer</I> keywords.
</P>
<P><B>Restrictions:</B>
</P>
<P>This pair style is part of the USER-SPH package. It is 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>, pair_sph/rhosum
</P>
<P><B>Default:</B> none
</P>
<HR>
<A NAME = "Monoghan"></A>
<P><B>(Monaghan)</B> Monaghan and Gingold, Journal of Computational Physics,
52, 374-389 (1983).
</P>
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