forked from lijiext/lammps
72 lines
2.6 KiB
Plaintext
72 lines
2.6 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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neighbor command :h3
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[Syntax:]
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neighbor skin style :pre
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skin = extra distance beyond force cutoff (distance units)
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style = {bin} or {nsq} or {multi} :ul
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[Examples:]
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neighbor 0.3 bin
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neighbor 2.0 nsq :pre
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[Description:]
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This command sets parameters that affect the building of the pairwise
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neighbor list. All atom pairs within a cutoff distance equal to the
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their force cutoff plus the {skin} distance are stored in the list.
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Typically, the larger the skin distance, the less often neighbor lists
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need to be built, but more pairs must be checked for possible force
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interactions every timestep. The default value for {skin} depends on
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the choice of units for the simulation (see below).
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The {style} value selects what algorithm is used to build the list.
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The {bin} style creates the list by binning which is an operation that
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scales linearly with N/P, the number of atoms per processor where N =
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total number of atoms and P = number of processors. It is almost
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always faster than the {nsq} style which scales as (N/P)^2. For
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unsolvated small molecules in a non-periodic box, the {nsq} choice can
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sometimes be faster. Either style should give the same answers.
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The {multi} style is a modified binning algorithm that is useful for
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systems with a wide range of cutoff distances, e.g. due to different
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size particles. For the {bin} style, the bin size is set to 1/2 of
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the largest cutoff distance between any pair of atom types and a
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single set of bins is defined to search over for all atom types. This
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can be inefficient if one pair of types has a very long cutoff, but
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other type pairs have a much shorter cutoff. For style {multi} the
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bin size is set to 1/2 of the shortest cutoff distance and multiple
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sets of bins are defined to search over for different atom types.
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This imposes some extra setup overhead, but the searches themselves
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may be much faster for the short-cutoff cases.
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The "neigh_modify"_neigh_modify.html command has additional options
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that control how often neighbor lists are built and which pairs are
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stored in the list.
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When a run is finished, counts of the number of neighbors stored in
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the pairwise list and the number of times neighbor lists were built
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are printed to the screen and log file. See "this
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section"_Section_start.html#2_7 for details.
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[Restrictions:] none
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[Related commands:]
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"neigh_modify"_neigh_modify.html, "units"_units.html
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[Default:]
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0.3 bin for lj units (0.3 sigma)
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2.0 bin for real or metal units (2.0 Angstroms) :pre
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