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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 morse command
</H3>
<H3>pair_style morse/gpu command
</H3>
<H3>pair_style morse/opt command
</H3>
<P><B>Syntax:</B>
</P>
<PRE>pair_style morse cutoff
</PRE>
<PRE>pair_style morse/gpu cutoff
</PRE>
<PRE>pair_style morse/opt cutoff
</PRE>
<UL><LI>cutoff = global cutoff for Morse interactions (distance units)
</UL>
<P><B>Examples:</B>
</P>
<PRE>pair_style morse 2.5
pair_style morse/opt 2.5
pair_coeff * * 100.0 2.0 1.5
pair_coeff 1 1 100.0 2.0 1.5 3.0
</PRE>
<P><B>Description:</B>
</P>
<P>Style <I>morse</I> computes pairwise interactions with the formula
</P>
<CENTER><IMG SRC = "Eqs/pair_morse.jpg">
</CENTER>
<P>Rc is the cutoff.
</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, 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>D0 (energy units)
<LI>alpha (1/distance units)
<LI>r0 (distance units)
<LI>cutoff (distance units)
</UL>
<P>The last coefficient is optional. If not specified, the global morse
cutoff is used.
</P>
<P>Style <I>morse/opt</I> is an optimized version of style <I>morse</I> that should
give identical answers. Depending on system size and the processor
you are running on, it may be 5-25% faster (for the pairwise portion
of the run time).
</P>
<P>Style <I>morse/gpu</I> is a GPU-enabled version of style <I>morse</I>.
See more details below.
</P>
<HR>
<P>The <I>morse/gpu</I> style is identical to the <I>morse</I> style,
except that each processor off-loads its pairwise calculations to a
GPU chip. Depending on the hardware available on your system this can provide a
speed-up. See the <A HREF = "Section_start.html#2_8">Running on GPUs</A> section of
the manual for more details about hardware and software requirements
for using GPUs.
</P>
<P>More details about these settings and various possible hardware
configuration are in <A HREF = "Section_start.html#2_8">this section</A> of the
manual.
</P>
<P>Additional requirements in your input script to run with GPU-enabled styles
are as follows:
</P>
<P>The <A HREF = "newton.html">newton pair</A> setting must be <I>off</I> and
<A HREF = "fix_gpu.html">fix gpu</A> must be used. The fix controls
the essential GPU selection and initialization steps.
</P>
<HR>
<P><B>Mixing, shift, table, tail correction, restart, rRESPA info</B>:
</P>
<P>None of these pair styles support mixing. Thus, coefficients for all
I,J pairs must be specified explicitly.
</P>
<P>All of these pair styles 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 options is not relevant for
the Morse pair styles.
</P>
<P>None of these pair styles support the <A HREF = "pair_modify.html">pair_modify</A>
tail option for adding long-range tail corrections to energy and
pressure.
</P>
<P>All of these pair styles write their 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>These pair styles can only be used via the <I>pair</I> keyword of the
<A HREF = "run_style.html">run_style respa</A> command. They do not support the
<I>inner</I>, <I>middle</I>, <I>outer</I> keywords.
</P>
<HR>
<P><B>Restrictions:</B>
</P>
<P>The <I>morse/opt</I> style is part of the "opt" package. The <I>morse/gpu</I>
style is part of the "gpu" package. They are only
enabled if LAMMPS was built with those packages. See the <A HREF = "Section_start.html#2_3">Making
LAMMPS</A> section for more info.
</P>
<P><B>Related commands:</B>
</P>
<P><A HREF = "pair_coeff.html">pair_coeff</A>
</P>
<P><B>Default:</B> none
</P>
</HTML>
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