forked from lijiext/lammps
181 lines
6.7 KiB
Plaintext
181 lines
6.7 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,Commands_all.html)
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:line
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pair_style lj/class2 command :h3
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pair_style lj/class2/gpu command :h3
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pair_style lj/class2/kk command :h3
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pair_style lj/class2/omp command :h3
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pair_style lj/class2/coul/cut command :h3
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pair_style lj/class2/coul/cut/kk command :h3
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pair_style lj/class2/coul/cut/omp command :h3
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pair_style lj/class2/coul/long command :h3
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pair_style lj/class2/coul/long/gpu command :h3
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pair_style lj/class2/coul/long/kk command :h3
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pair_style lj/class2/coul/long/omp command :h3
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[Syntax:]
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pair_style style args :pre
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style = {lj/class2} or {lj/class2/coul/cut} or {lj/class2/coul/long}
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args = list of arguments for a particular style :ul
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{lj/class2} args = cutoff
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cutoff = global cutoff for class 2 interactions (distance units)
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{lj/class2/coul/cut} args = cutoff (cutoff2)
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cutoff = global cutoff for class 2 (and Coulombic if only 1 arg) (distance units)
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cutoff2 = global cutoff for Coulombic (optional) (distance units)
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{lj/class2/coul/long} args = cutoff (cutoff2)
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cutoff = global cutoff for class 2 (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 lj/class2 10.0
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pair_coeff * * 100.0 2.5
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pair_coeff 1 2* 100.0 2.5 9.0 :pre
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pair_style lj/class2/coul/cut 10.0
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pair_style lj/class2/coul/cut 10.0 8.0
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pair_coeff * * 100.0 3.0
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pair_coeff 1 1 100.0 3.5 9.0
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pair_coeff 1 1 100.0 3.5 9.0 9.0 :pre
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pair_style lj/class2/coul/long 10.0
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pair_style lj/class2/coul/long 10.0 8.0
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pair_coeff * * 100.0 3.0
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pair_coeff 1 1 100.0 3.5 9.0 :pre
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[Description:]
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The {lj/class2} styles compute a 6/9 Lennard-Jones potential given by
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:c,image(Eqs/pair_class2.jpg)
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Rc is the cutoff.
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The {lj/class2/coul/cut} and {lj/class2/coul/long} styles add a
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Coulombic term as described for the "lj/cut"_pair_lj.html pair styles.
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See "(Sun)"_#pair-Sun for a description of the COMPASS class2 force field.
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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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epsilon (energy units)
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sigma (distance units)
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cutoff1 (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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class 2 and Coulombic cutoffs are used. If only one cutoff is
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specified, it is used as the cutoff for both class 2 and Coulombic
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interactions for this type pair. If both coefficients are specified,
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they are used as the class 2 and Coulombic cutoffs for this type pair.
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You cannot specify 2 cutoffs for style {lj/class2}, since it has no
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Coulombic terms.
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For {lj/class2/coul/long} only the class 2 cutoff can be specified
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since a Coulombic cutoff cannot be specified for an individual I,J
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type pair. All type pairs use the same global Coulombic cutoff
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specified in the pair_style command.
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:line
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If the pair_coeff command is not used to define coefficients for a
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particular I != J type pair, the mixing rule for epsilon and sigma for
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all class2 potentials is to use the {sixthpower} formulas documented
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by the "pair_modify"_pair_modify.html command. The "pair_modify
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mix"_pair_modify.html setting is thus ignored for class2 potentials
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for epsilon and sigma. However it is still followed for mixing the
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cutoff distance.
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:line
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A version of these styles with a soft core, {lj/cut/soft}, suitable for use in
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free energy calculations, is part of the USER-FEP package and is documented with
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the "pair_fep_soft"_pair_fep_soft.html styles. The version with soft core is
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only available if LAMMPS was built with that package. See the "Build
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package"_Build_package.html doc page for more info.
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:line
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Styles with a {gpu}, {intel}, {kk}, {omp}, or {opt} 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 on the "Speed packages"_Speed_packages.html doc
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page. The accelerated styles take the same arguments and should
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produce the same results, except for round-off and precision issues.
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These accelerated styles are part of the GPU, USER-INTEL, KOKKOS,
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USER-OMP and OPT packages, respectively. They are only enabled if
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LAMMPS was built with those packages. See the "Build
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package"_Build_package.html doc page 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"_Run_options.html when you invoke LAMMPS, or you can use the
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"suffix"_suffix.html command in your input script.
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See the "Speed packages"_Speed_packages.html doc page 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 epsilon and sigma coefficients
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and cutoff distance for all of the lj/class2 pair styles can be mixed.
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Epsilon and sigma are always mixed with the value {sixthpower}. The
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cutoff distance is mixed by whatever option is set by the pair_modify
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command (default = geometric). See the "pair_modify" command for
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details.
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All of the lj/class2 pair styles support the
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"pair_modify"_pair_modify.html shift option for the energy of the
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Lennard-Jones portion of the pair interaction.
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The {lj/class2/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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All of the lj/class2 pair styles support the
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"pair_modify"_pair_modify.html tail option for adding a long-range
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tail correction to the energy and pressure of the Lennard-Jones
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portion of the pair interaction.
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All of the lj/class2 pair styles write their information to "binary
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restart files"_restart.html, so pair_style and pair_coeff commands do
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not need to be specified in an input script that reads a restart file.
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Only the {lj/class2} and {lj/class2/coul/long} pair styles support the use of the
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{inner}, {middle}, and {outer} keywords of the "run_style
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respa"_run_style.html command, meaning the pairwise forces can be
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partitioned by distance at different levels of the rRESPA hierarchy.
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The other styles only support the {pair} keyword of run_style respa.
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See the "run_style"_run_style.html command for details.
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[Restrictions:]
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These styles are part of the CLASS2 package. They are only enabled if
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LAMMPS was built with that package. See the "Build
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package"_Build_package.html doc page for more info.
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[Related commands:]
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"pair_coeff"_pair_coeff.html, "pair_fep_soft"_pair_fep_soft.html
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[Default:] none
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:line
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:link(pair-Sun)
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[(Sun)] Sun, J Phys Chem B 102, 7338-7364 (1998).
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