forked from lijiext/lammps
154 lines
5.2 KiB
Plaintext
154 lines
5.2 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 coul/cut command :h3
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pair_style coul/cut/omp command :h3
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pair_style coul/debye command :h3
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pair_style coul/debye/omp command :h3
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pair_style coul/long command :h3
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pair_style coul/long/omp command :h3
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pair_style coul/long/gpu command :h3
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[Syntax:]
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pair_style coul/cut cutoff
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pair_style coul/debye kappa cutoff
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pair_style coul/long cutoff
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pair_style coul/long/gpu cutoff :pre
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cutoff = global cutoff for Coulombic interactions
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kappa = Debye length (inverse distance units) :ul
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[Examples:]
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pair_style coul/cut 2.5
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pair_coeff * *
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pair_coeff 2 2 3.5 :pre
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pair_style coul/debye 1.4 3.0
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pair_coeff * *
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pair_coeff 2 2 3.5 :pre
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pair_style coul/long 10.0
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pair_coeff * * :pre
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[Description:]
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The {coul/cut} style computes the standard Coulombic interaction
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potential given by
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:c,image(Eqs/pair_coulomb.jpg)
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where C is an energy-conversion constant, Qi and Qj are the charges on
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the 2 atoms, and epsilon is the dielectric constant which can be set
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by the "dielectric"_dielectric.html command. The cutoff Rc truncates
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the interaction distance.
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Style {coul/debye} adds an additional exp() damping factor to the
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Coulombic term, given by
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:c,image(Eqs/pair_debye.jpg)
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where kappa is the Debye length. This potential is another way to
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mimic the screening effect of a polar solvent.
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Style {coul/long} computes the same Coulombic interactions as style
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{coul/cut} except that an additional damping factor is applied so it
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can be used in conjunction with the "kspace_style"_kspace_style.html
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command and its {ewald} or {pppm} option. The Coulombic cutoff
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specified for this style means that pairwise interactions within this
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distance are computed directly; interactions outside that distance are
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computed in reciprocal space.
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These potentials are designed to be combined with other pair
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potentials via the "pair_style hybrid/overlay"_pair_hybrid.html
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command. This is because they have no repulsive core. Hence if they
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are used by themselves, there will be no repulsion to keep two
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oppositely charged particles from overlapping each other.
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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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cutoff (distance units) :ul
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For {coul/cut} and {coul/debye}, the cutoff coefficient is optional.
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If it is not used (as in some of the examples above), the default
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global value specified in the pair_style command is used.
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For {coul/long} no cutoff can be specified for an individual I,J type
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pair via the pair_coeff command. 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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Styles with a {cuda}, {gpu}, {omp}, or {opt} suffix are functionally
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the same as the corresponding style without the suffix. They have
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been optimized to run faster, depending on your available hardware,
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as discussed in "this section"_Section_accelerate.html of the manual.
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The accelerated styles take the same arguments and should produce the
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same results, except for round-off and precision issues.
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These accelerated styles are part of the USER-CUDA, GPU, USER-OMP and OPT
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packages, respectively. They are only enabled if LAMMPS was built with
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those packages. See the "Making LAMMPS"_Section_start.html#start_3
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section for more info.
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You can specify the accelerated styles explicitly in your input script
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by including their suffix, or you can use the "-suffix command-line
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switch"_Section_start.html#start_6 when you invoke LAMMPS, or you can
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use the "suffix"_suffix.html command in your input script.
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See "this section"_Section_accelerate.html of the manual for more
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instructions on how to use the accelerated styles effectively.
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:line
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[Mixing, shift, table, tail correction, restart, rRESPA info]:
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For atom type pairs I,J and I != J, the cutoff distance for the
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{coul/cut} style can be mixed. The default mix value is {geometric}.
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See the "pair_modify" command for details.
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The "pair_modify"_pair_modify.html shift option is not relevant
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for these pair styles.
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The {coul/long} style supports the "pair_modify"_pair_modify.html
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table option for tabulation of the short-range portion of the
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long-range Coulombic interaction.
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These pair styles do not support the "pair_modify"_pair_modify.html
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tail option for adding long-range tail corrections to energy and
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pressure.
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These pair styles write their information to "binary restart
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files"_restart.html, 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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This pair style can only be used via the {pair} keyword of the
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"run_style respa"_run_style.html command. It does not support the
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{inner}, {middle}, {outer} keywords.
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:line
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[Restrictions:]
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The {coul/long} style is part of the KSPACE package. It is only
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enabled if LAMMPS was built with that package (which it is by
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default). See the "Making LAMMPS"_Section_start.html#start_3 section
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for more info.
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[Related commands:]
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"pair_coeff"_pair_coeff.html, "pair_style
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hybrid/overlay"_pair_hybrid.html
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[Default:] none
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