2006-09-22 00:22:34 +08:00
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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/smooth command :h3
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[Syntax:]
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pair_style lj/smooth Rin cutoff :pre
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Rin = global inner cutoff beyond which force smoothing will be applied (distance units)
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cutoff = global cutoff for lj/smooth interactions (distance units) :ul
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[Examples:]
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pair_style lj/smooth 8.0 10.0
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pair_coeff * * 10.0 1.5
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pair_coeff 1 1 20.0 1.3 7.0 9.0 :pre
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[Description:]
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Style {lj/smooth} computes a LJ interaction with a force smoothing
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applied between the inner and outer cutoff.
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:c,image(Eqs/pair_lj_smooth.jpg)
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The polynomial coefficients C1, C2, C3, C4 are computed by LAMMPS to
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cause the force to vary smoothly from Rin to Rc. At Rin the force and
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its 1st derivative will match the unsmoothed LJ formula. At Rc the
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2007-02-20 02:03:15 +08:00
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force and its 1st derivative will be 0.0.
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IMPORTANT NOTE: this force smoothing causes the energy to be
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discontinuous both in its values and 1st derivative. This can lead to
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poor energy conservation and may require the use of a thermostat.
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Plot the energy and force resulting from this formula via the
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2006-09-22 00:22:34 +08:00
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"pair_write"_pair_write.html command to see the effect.
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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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Rin (distance units)
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cutoff (distance units) :ul
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The last 2 coefficients are optional. If not specified, the global
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Rin and cutoff are used. Rin cannot be 0.0. If Rin = cutoff, then no
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force smoothing is performed for this type pair; the standard LJ
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formula is used.
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[Restrictions:] none
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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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