forked from lijiext/lammps
137 lines
4.9 KiB
HTML
137 lines
4.9 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 born command
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</H3>
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<H3>pair_style born/coul/long 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 style args
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</PRE>
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<UL><LI>style = <I>born</I> or <I>born/coul/long</I>
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<LI>args = list of arguments for a particular style
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</UL>
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<PRE> <I>born</I> args = cutoff
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cutoff = global cutoff for non-Coulombic interactions (distance units)
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<I>born/coul/long</I> args = cutoff (cutoff2)
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cutoff = global cutoff for non-Coulombic (and Coulombic if only 1 arg) (distance units)
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cutoff2 = global cutoff for Coulombic (optional) (distance units)
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</PRE>
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<P><B>Examples:</B>
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</P>
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<PRE>pair_style born 10.0
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pair_coeff * * 6.08 0.317 2.340 24.18 11.51
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pair_coeff 1 1 6.08 0.317 2.340 24.18 11.51
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</PRE>
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<PRE>pair_style born/coul/long 10.0
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pair_style born/coul/long 10.0 8.0
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pair_coeff * * 6.08 0.317 2.340 24.18 11.51
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pair_coeff 1 1 6.08 0.317 2.340 24.18 11.51
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</PRE>
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<P><B>Description:</B>
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</P>
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<P>The <I>born</I> style computes the Born-Mayer-Huggins or Tosi/Fumi
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potential described in <A HREF = "#FumiTosi">(Fumi and Tosi)</A>, given by
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</P>
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<CENTER><IMG SRC = "Eqs/pair_born.jpg">
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</CENTER>
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<P>where sigma is an interaction-dependent length parameter, rho is an
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ionic-pair dependent length parameter, and Rc is the cutoff.
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</P>
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<P>The <I>born/coul/long</I> style adds a Coulombic term as described for the
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<A HREF = "pair_lj.html">lj/cut</A> pair styles. An additional damping factor is
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applied to the Coulombic term so it can be used in conjunction with
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the <A HREF = "kspace_style.html">kspace_style</A> command and its <I>ewald</I> or <I>pppm</I>
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option. The Coulombic cutoff specified for this style means that
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pairwise interactions within this distance are computed directly;
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interactions outside that distance are computed in reciprocal space.
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</P>
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<P>If one cutoff is specified for the <I>born/coulk/long</I> style, it is used
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for both the A,C,D and Coulombic terms. If two cutoffs are specified,
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the first is used as the cutoff for the A,C,D terms, and the second is
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the cutoff for the Coulombic term.
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</P>
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<P>Note that these potentials are related to the <A HREF = "pair_born.html">Buckingham
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potential</A>.
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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>A (energy units)
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<LI>rho (distance units)
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<LI>sigma (distance units)
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<LI>C (energy units * distance units^6)
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<LI>D (energy units * distance units^8)
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<LI>cutoff (distance units)
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</UL>
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<P>The second coefficient, rho, must be greater than zero.
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</P>
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<P>The last coefficient is optional. If not specified, the global A,C,D
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cutoff specified in the pair_style command is used.
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</P>
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<P>For <I>buck/coul/long</I> no Coulombic cutoff can be specified for an
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individual I,J type pair. All type pairs use the same global
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Coulombic cutoff specified in the pair_style command.
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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>These pair styles do not 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>These styles support the <A HREF = "pair_modify.html">pair_modify</A> shift option
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for the energy of the exp(), 1/r^6, and 1/r^8 portion of the pair
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interaction.
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</P>
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<P>The <I>born/coul/long</I> pair style does not support the
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<A HREF = "pair_modify.html">pair_modify</A> table option since a tabulation
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capability has not yet been added to this potential.
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</P>
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<P>These styles support the pair_modify tail option for adding long-range
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tail corrections to energy and pressure.
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</P>
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<P>Thess styles writes thei information to binary <A HREF = "restart.html">restart</A>
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files, so pair_style and pair_coeff commands do not need to be
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specified in an input script that reads a restart file.
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</P>
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<P>These styles can only be used via the <I>pair</I> keyword of the <A HREF = "run_style.html">run_style
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respa</A> command. They do not support the <I>inner</I>,
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<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>born/coul/long</I> style is part of the "kspace" package. It is
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only enabled if LAMMPS was built with that package (which it is by
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default). See the <A HREF = "Section_start.html#2_3">Making LAMMPS</A> section for
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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>, <A HREF = "pair_buck.html">pair_style buck</A>
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</P>
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<P><B>Default:</B> none
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</P>
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<HR>
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<A NAME = "FumiTosi"></A>
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<P>Fumi and Tosi, J Phys Chem Solids, 25, 31 (1964),
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Fumi and Tosi, J Phys Chem Solids, 25, 45 (1964).
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</P>
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</HTML>
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