2006-09-22 00:22:34 +08:00
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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>
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<HR>
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<H3>pair_style morse command
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</H3>
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2007-02-10 05:40:32 +08:00
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<H3>pair_style morse/opt command
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</H3>
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2006-09-22 00:22:34 +08:00
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<P><B>Syntax:</B>
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</P>
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<PRE>pair_style morse cutoff
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</PRE>
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<UL><LI>cutoff = global cutoff for Morse interactions (distance units)
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</UL>
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<P><B>Examples:</B>
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</P>
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<PRE>pair_style morse 2.5
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2007-02-10 05:40:32 +08:00
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pair_style morse/opt 2.5
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2006-09-22 00:22:34 +08:00
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pair_coeff * * 100.0 2.0 1.5
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pair_coeff 1 1 100.0 2.0 1.5 3.0
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</PRE>
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<P><B>Description:</B>
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</P>
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<P>Style <I>morse</I> computes pairwise interactions with the formula
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</P>
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<CENTER><IMG SRC = "Eqs/pair_morse.jpg">
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</CENTER>
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<P>Rc is the cutoff.
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</P>
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<P>The following coefficients must be defined for each pair of atoms
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types via the <A HREF = "pair_coeff.html">pair_coeff</A> command as in the examples
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above, or in the data file or restart files read by the
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<A HREF = "read_data.html">read_data</A> or <A HREF = "read_restart.html">read_restart</A>
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commands:
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</P>
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<UL><LI>D0 (energy units)
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<LI>alpha (1/distance units)
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<LI>r0 (distance units)
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<LI>cutoff (distance units)
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</UL>
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<P>The last coefficient is optional. If not specified, the global morse
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cutoff is used.
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</P>
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2007-02-10 05:40:32 +08:00
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<P>Style <I>morse/opt</I> is an optimized version of style <I>morse</I> that should
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give identical answers. Depending on system size and the processor
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you are running on, it may be 5-25% faster (for the pairwise portion
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of the run time).
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</P>
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2007-06-26 08:03:39 +08:00
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<HR>
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2007-10-04 08:21:14 +08:00
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<P><B>Mixing, shift, table, tail correction, per-atom energy/stress,
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restart, rRESPA info</B>:
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2007-06-26 08:03:39 +08:00
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</P>
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<P>None of the Morse pair styles support mixing. Thus, coefficients for
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all I,J pairs must be specified explicitly.
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</P>
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<P>All of the Morse pair styles support the
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<A HREF = "pair_modify.html">pair_modify</A> shift option for the energy of the pair
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interaction.
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</P>
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<P>The <A HREF = "pair_modify.html">pair_modify</A> table options is not relevant for
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the Morse pair styles.
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2006-09-28 03:12:31 +08:00
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</P>
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2007-06-26 08:03:39 +08:00
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<P>None of the Morse pair styles support the
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<A HREF = "pair_modify.html">pair_modify</A> tail option for adding long-range tail
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corrections to energy and pressure.
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</P>
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<P>All of the Morse pair styles can calculate per-atom energy and
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stress, as used by the <A HREF = "compute_epair_atom.html">compute epair/atom</A>,
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<A HREF = "compute_stress_atom.html">compute stress/atom</A>, and <A HREF = "dump.html">dump
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custom</A> commands.
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</P>
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<P>All of the Morse pair styles write their information to <A HREF = "restart.html">binary
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restart files</A>, so pair_style and pair_coeff commands do
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not need to be specified in an input script that reads a restart file.
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</P>
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2007-10-04 08:21:14 +08:00
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<P>This pair style can only be used via the <I>pair</I> keyword of the
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<A HREF = "run_style.html">run_style respa</A> command. It does not support the
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2007-10-12 07:09:49 +08:00
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<I>inner</I>, <I>middle</I>, <I>outer</I> keywords.
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2007-10-04 08:21:14 +08:00
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</P>
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2007-06-26 08:03:39 +08:00
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<HR>
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<P><B>Restrictions:</B>
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2006-09-22 00:22:34 +08:00
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</P>
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2007-02-10 05:40:32 +08:00
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<P>The <I>morse/opt</I> style is part of the "opt" package. It is only
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enabled if LAMMPS was built with that package. See the <A HREF = "Section_start.html#2_3">Making
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LAMMPS</A> section for more info.
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</P>
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2006-09-22 00:22:34 +08:00
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<P><B>Related commands:</B>
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</P>
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<P><A HREF = "pair_coeff.html">pair_coeff</A>
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</P>
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<P><B>Default:</B> none
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</P>
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</HTML>
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