forked from lijiext/lammps
130 lines
4.2 KiB
Plaintext
130 lines
4.2 KiB
Plaintext
"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 born command :h3
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pair_style born/coul/long command :h3
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[Syntax:]
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pair_style style args :pre
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style = {born} or {born/coul/long}
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args = list of arguments for a particular style :ul
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{born} args = cutoff
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cutoff = global cutoff for non-Coulombic interactions (distance units)
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{born/coul/long} 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) :pre
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[Examples:]
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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 :pre
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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 :pre
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[Description:]
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The {born} style computes the Born-Mayer-Huggins or Tosi/Fumi
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potential described in "(Fumi and Tosi)"_#FumiTosi, given by
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:c,image(Eqs/pair_born.jpg)
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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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The {born/coul/long} style adds a Coulombic term as described for the
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"lj/cut"_pair_lj.html 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 "kspace_style"_kspace_style.html command and its {ewald} or {pppm}
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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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If one cutoff is specified for the {born/coulk/long} 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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Note that these potentials are related to the "Buckingham
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potential"_pair_born.html.
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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, or by mixing as described below:
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A (energy units)
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rho (distance units)
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sigma (distance units)
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C (energy units * distance units^6)
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D (energy units * distance units^8)
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cutoff (distance units) :ul
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The second coefficient, rho, must be greater than zero.
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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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For {buck/coul/long} 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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:line
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[Mixing, shift, table, tail correction, restart, rRESPA info]:
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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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These styles support the "pair_modify"_pair_modify.html 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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The {born/coul/long} pair style does not support the
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"pair_modify"_pair_modify.html table option since a tabulation
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capability has not yet been added to this potential.
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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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Thess styles writes thei information to binary "restart"_restart.html
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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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These styles can only be used via the {pair} keyword of the "run_style
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respa"_run_style.html command. They do not support the {inner},
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{middle}, {outer} keywords.
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:line
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[Restrictions:]
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The {born/coul/long} 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 "Making LAMMPS"_Section_start.html#2_3 section for
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more info.
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[Related commands:]
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"pair_coeff"_pair_coeff.html, "pair_style buck"_pair_buck.html
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[Default:] none
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:line
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:link(FumiTosi)
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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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