forked from lijiext/lammps
121 lines
4.3 KiB
HTML
121 lines
4.3 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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</CENTER>
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<HR>
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<H3>pair_style lj/expand command
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</H3>
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<H3>pair_style lj/expand/cuda command
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</H3>
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<H3>pair_style lj/expand/gpu command
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</H3>
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<H3>pair_style lj/expand/omp 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 lj/expand cutoff
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</PRE>
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<UL><LI>cutoff = global cutoff for lj/expand 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 lj/expand 2.5
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pair_coeff * * 1.0 1.0 0.5
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pair_coeff 1 1 1.0 1.0 -0.2 2.0
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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>lj/expand</I> computes a LJ interaction with a distance shifted by
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delta which can be useful when particles are of different sizes, since
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it is different that using different sigma values in a standard LJ
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formula:
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</P>
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<CENTER><IMG SRC = "Eqs/pair_lj_expand.jpg">
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</CENTER>
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<P>Rc is the cutoff which does not include the delta distance. I.e. the
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actual force cutoff is the sum of cutoff + delta.
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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, or by mixing as described below:
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</P>
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<UL><LI>epsilon (energy units)
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<LI>sigma (distance units)
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<LI>delta (distance units)
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<LI>cutoff (distance units)
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</UL>
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<P>The delta values can be positive or negative. The last coefficient is
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optional. If not specified, the global LJ cutoff is used.
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</P>
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<HR>
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<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
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functionally the same as the corresponding style without the suffix.
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They have been optimized to run faster, depending on your available
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hardware, as discussed in <A HREF = "Section_accelerate.html">Section_accelerate</A>
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of the manual. The accelerated styles take the same arguments and
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should produce the same results, except for round-off and precision
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issues.
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</P>
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<P>These accelerated styles are part of the USER-CUDA, GPU, USER-INTEL,
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KOKKOS, USER-OMP and OPT packages, respectively. They are only
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enabled if LAMMPS was built with those packages. See the <A HREF = "Section_start.html#start_3">Making
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LAMMPS</A> section for more info.
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</P>
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<P>You can specify the accelerated styles explicitly in your input script
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by including their suffix, or you can use the <A HREF = "Section_start.html#start_7">-suffix command-line
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switch</A> when you invoke LAMMPS, or you can
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use the <A HREF = "suffix.html">suffix</A> command in your input script.
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</P>
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<P>See <A HREF = "Section_accelerate.html">Section_accelerate</A> of the manual for
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more instructions on how to use the accelerated styles effectively.
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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>For atom type pairs I,J and I != J, the epsilon, sigma, and shift
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coefficients and cutoff distance for this pair style can be mixed.
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Shift is always mixed via an <I>arithmetic</I> rule. The other
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coefficients are mixed according to the pair_modify mix value. The
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default mix value is <I>geometric</I>. See the "pair_modify" command for
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details.
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</P>
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<P>This pair style supports the <A HREF = "pair_modify.html">pair_modify</A> shift
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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 option is not relevant
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for this pair style.
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</P>
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<P>This pair style supports the <A HREF = "pair_modify.html">pair_modify</A> tail
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option for adding a long-range tail correction to the energy and
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pressure of the pair interaction.
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</P>
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<P>This pair style writes its 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>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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<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> none
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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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