forked from lijiext/lammps
90 lines
2.8 KiB
Plaintext
90 lines
2.8 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 soft command :h3
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[Syntax:]
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pair_style soft cutoff :pre
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cutoff = global cutoff for soft interactions (distance units) :ul
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[Examples:]
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pair_style soft 2.5
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pair_coeff * * 0.0 60.0
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pair_coeff 1 1 0.0 60.0 3.0 :pre
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[Description:]
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Style {soft} computes pairwise interactions with the formula
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:c,image(Eqs/pair_soft.jpg)
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It is useful for pushing apart overlapping atoms, since it does not
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blow up as r goes to 0. A is a pre-factor that varies in time from
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the start to the end of the run. The "run"_run.html command documents
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how to make the ramping take place across multiple runs. Rc is the
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cutoff. See the "fix nve/limit"_fix_nve_limit.html command for
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another way to push apart overlapping atoms.
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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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Astart (energy units)
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Astop (energy units)
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cutoff (distance units) :ul
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Astart and Astop are the values of the prefactor at the start and end
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of the next run. At intermediate times the value of A will be ramped
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between these 2 values. Note that before performing a 2nd run, you
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will want to adjust the values of Astart and Astop for all type pairs,
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or switch to a new pair style.
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The last coefficient is optional. If not specified, the global soft
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cutoff is used.
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:line
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[Mixing, shift, table, tail correction, per-atom energy/stress, and
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restart info]:
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For atom type pairs I,J and I != J, the Astart, Astop coefficients and
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cutoff distance for this pair style can be mixed. Astart and Atop are
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always mixed via a {geometric} rule. The cutoff is mixed according to
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the pair_modify mix value. The default mix value is {geometric}. See
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the "pair_modify" command for details.
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This pair styles does not support the "pair_modify"_pair_modify.html
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shift option, since the pair interaction is goes to 0.0 at the cutoff.
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The "pair_modify"_pair_modify.html table and tail options are not
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relevant for this pair style.
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This pair style can calculate per-atom energy and stress, as used by
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the "compute epair/atom"_compute_epair_atom.html, "compute
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stress/atom"_compute_stress_atom.html, and "dump custom"_dump.html
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commands.
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This pair style writes its 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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:line
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[Restrictions:] none
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[Related commands:]
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"pair_coeff"_pair_coeff.html, "fix nve/limit"_fix_nve_limit.html
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[Default:] none
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