forked from lijiext/lammps
104 lines
3.2 KiB
Plaintext
104 lines
3.2 KiB
Plaintext
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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 lj/class2 command :h3
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pair_style lj/class2/coul/cut command :h3
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pair_style lj/class2/coul/long 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
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styles.
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See "(Sun)"_#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:
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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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[Restrictions:]
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These styles are part of the "class2" package. They are only enabled
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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 {lj/class2/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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:line
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:link(Sun)
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[(Sun)] Sun, J Phys Chem B 102, 7338-7364 (1998).
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