2006-09-22 00:22:34 +08:00
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"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c
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:link(lws,http://lammps.sandia.gov)
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:link(ld,Manual.html)
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:link(lc,Section_commands.html#comm)
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:line
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pair_style buck command :h3
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pair_style buck/coul/cut command :h3
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pair_style buck/coul/long command :h3
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[Syntax:]
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pair_style style args :pre
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style = {buck} or {buck/coul/cut} or {buck/coul/long}
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args = list of arguments for a particular style :ul
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{buck} args = cutoff
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cutoff = global cutoff for Buckingham interactions (distance units)
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{buck/coul/cut} args = cutoff (cutoff2)
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cutoff = global cutoff for Buckingham (and Coulombic if only 1 arg) (distance units)
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cutoff2 = global cutoff for Coulombic (optional) (distance units)
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{buck/coul/long} args = cutoff (cutoff2)
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cutoff = global cutoff for Buckingham (and Coulombic if only 1 arg) (distance units)
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cutoff2 = global cutoff for Coulombic (optional) (distance units) :pre
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[Examples:]
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pair_style buck 2.5
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pair_coeff * * 100.0 1.5 200.0
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pair_coeff * * 100.0 1.5 200.0 3.0 :pre
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pair_style buck/coul/cut 10.0
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pair_style buck/coul/cut 10.0 8.0
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pair_coeff * * 100.0 1.5 200.0
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pair_coeff 1 1 100.0 1.5 200.0 9.0
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pair_coeff 1 1 100.0 1.5 200.0 9.0 8.0 :pre
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pair_style buck/coul/long 10.0
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pair_style buck/coul/long 10.0 8.0
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pair_coeff * * 100.0 1.5 200.0
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pair_coeff 1 1 100.0 1.5 200.0 9.0 :pre
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[Description:]
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The {buck} style computes a Buckingham potential (exp/6 instead of
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Lennard-Jones 12/6) given by
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:c,image(Eqs/pair_buck.jpg)
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Rc is the cutoff.
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The {buck/coul/cut} and {buck/coul/long} styles add a Coulombic term
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as described for the "lj/cut"_pair_style_lj.html pair styles.
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The following coefficients must be defined for each pair of atoms
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types via the "pair_coeff"_pair_coeff.html 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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"read_data"_read_data.html or "read_restart"_read_restart.html
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commands:
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A (energy units)
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rho (distance units)
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C (energy-distance^6 units)
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cutoff (distance units)
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cutoff2 (distance units) :ul
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The latter 2 coefficients are optional. If not specified, the global
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LJ and Coulombic cutoffs are used. If only one cutoff is specified,
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it is used as the cutoff for both LJ and Coulombic interactions for
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this type pair. If both coefficients are specified, they are used as
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the LJ and Coulombic cutoffs for this type pair. You cannot specify 2
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cutoffs for style {buck}, since it has no Coulombic terms.
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For {buck/coul/long} only the LJ cutoff can be specified since a
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Coulombic cutoff cannot be specified for an individual I,J type pair.
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All type pairs use the same global Coulombic cutoff specified in the
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pair_style command.
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[Restrictions:]
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2006-09-28 03:12:31 +08:00
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The {buck} potentials do not support the
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"pair_modify"_pair_modify.hmtl {mix} option. Coefficients for all i,j
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pairs must be specified explicitly.
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2006-09-22 00:22:34 +08:00
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The {buck/coul/long} style is part of the "kspace" package. It is
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only enabled if LAMMPS was built with that package. See the "Making
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LAMMPS"_Section_start.html#2_2 section for more info.
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On some 64-bit machines, compiling with -O3 appears to break the
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Coulombic tabling option used by the {buck/coul/long} style. See
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the "Additional build tips" section of the Making LAMMPS documentation
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pages for workarounds on this issue.
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[Related commands:]
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"pair_coeff"_pair_coeff.html
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[Default:] none
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