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<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>pair_style beck command
</H3>
<H3>pair_style beck/gpu command
</H3>
<H3>pair_style beck/omp command
</H3>
<P><B>Syntax:</B>
</P>
<PRE>pair_style beck Rc
</PRE>
<UL><LI>Rc = cutoff for interactions (distance units)
</UL>
<P><B>Examples:</B>
</P>
<PRE>pair_style beck 8.0
pair_coeff * * 399.671876712 0.0000867636112694 0.675 4.390 0.0003746
pair_coeff 1 1 399.671876712 0.0000867636112694 0.675 4.390 0.0003746 6.0
</PRE>
<P><B>Description:</B>
</P>
<P>Style <I>beck</I> computes interactions based on the potential by
<A HREF = "#Beck">(Beck)</A>, originally designed for simulation of Helium. It
includes truncation at a cutoff distance Rc.
</P>
<CENTER><IMG SRC = "Eqs/pair_beck.jpg">
</CENTER>
<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, or in the data file or restart files read by the
<A HREF = "read_data.html">read_data</A> or <A HREF = "read_restart.html">read_restart</A>
commands.
</P>
<UL><LI>A (energy units)
<LI>B (energy-distance^6 units)
<LI>a (distance units)
<LI>alpha (1/distance units)
<LI>beta (1/distance^6 units)
<LI>cutoff (distance units)
</UL>
<P>The last coefficient is optional. If not specified, the global cutoff
Rc is used.
</P>
<HR>
<P>Styles with a <I>cuda</I>, <I>gpu</I>, <I>intel</I>, <I>kk</I>, <I>omp</I>, or <I>opt</I> suffix are
functionally the same as the corresponding style without the suffix.
They have been optimized to run faster, depending on your available
hardware, as discussed in <A HREF = "Section_accelerate.html">Section_accelerate</A>
of the manual. The accelerated styles take the same arguments and
should produce the same results, except for round-off and precision
issues.
</P>
<P>These accelerated styles are part of the USER-CUDA, GPU, USER-INTEL,
KOKKOS, USER-OMP and OPT packages, respectively. They are only
enabled if LAMMPS was built with those packages. See the <A HREF = "Section_start.html#start_3">Making
LAMMPS</A> section for more info.
</P>
<P>You can specify the accelerated styles explicitly in your input script
by including their suffix, or you can use the <A HREF = "Section_start.html#start_7">-suffix command-line
switch</A> when you invoke LAMMPS, or you can
use the <A HREF = "suffix.html">suffix</A> command in your input script.
</P>
<P>See <A HREF = "Section_accelerate.html">Section_accelerate</A> of the manual for
more instructions on how to use the accelerated styles effectively.
</P>
<HR>
<P><B>Mixing, shift, table, tail correction, restart, rRESPA info</B>:
</P>
<P>For atom type pairs I,J and I != J, coeffiecients must be specified.
No default miture rules are used.
</P>
<P>This pair style does not support the <A HREF = "pair_modify.html">pair_modify</A> shift
option for the energy of the pair interaction.
</P>
<P>The <A HREF = "pair_modify.html">pair_modify</A> table option is not relevant
for this pair style.
</P>
<P>This pair style does not support the <A HREF = "pair_modify.html">pair_modify</A>
tail option for adding long-range tail corrections.
</P>
<P>This pair style writes its information to <A HREF = "restart.html">binary restart
files</A>, so pair_style and pair_coeff commands do not need
to be specified in an input script that reads a restart file.
</P>
<P>This pair 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>
<HR>
<P><B>Restrictions:</B> none
</P>
<P><B>Related commands:</B>
</P>
<P><A HREF = "pair_coeff.html">pair_coeff</A>
</P>
<P><B>Default:</B> none
</P>
<HR>
<A NAME = "Beck"></A>
<P><B>(Beck)</B> Beck, Molecular Physics, 14, 311 (1968).
</P>
</HTML>
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