forked from lijiext/lammps
96 lines
2.9 KiB
HTML
96 lines
2.9 KiB
HTML
<HTML>
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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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<H3>pair_style morse/opt command
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</H3>
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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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pair_style morse/opt 2.5
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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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<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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<HR>
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<P><B>Mixing, shift, table, tail correction, restart, rRESPA info</B>:
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</P>
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<P>None of these pair styles support mixing. Thus, coefficients for all
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I,J pairs must be specified explicitly.
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</P>
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<P>All of these pair styles support the <A HREF = "pair_modify.html">pair_modify</A>
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shift option for the energy of the pair 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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</P>
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<P>None of these pair styles support the <A HREF = "pair_modify.html">pair_modify</A>
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tail option for adding long-range tail corrections to energy and
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pressure.
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</P>
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<P>All of these pair styles write their information to <A HREF = "restart.html">binary restart
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files</A>, so pair_style and pair_coeff commands do not need
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to be specified in an input script that reads a restart file.
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</P>
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<P>These pair styles 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. They do not support the
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<I>inner</I>, <I>middle</I>, <I>outer</I> keywords.
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</P>
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<HR>
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<P><B>Restrictions:</B>
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</P>
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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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<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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