"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c

:link(lws,http://lammps.sandia.gov)
:link(ld,Manual.html)
:link(lc,Section_commands.html#comm)

:line

pair_style born/coul/long/cs command :h3
pair_style buck/coul/long/cs command :h3
pair_style born/coul/dsf/cs command :h3

[Syntax:]

pair_style style args :pre

style = {born/coul/long/cs} or {buck/coul/long/cs} or {born/coul/dsf/cs}
args = list of arguments for a particular style :ul
  {born/coul/long/cs} args = cutoff (cutoff2)
    cutoff = global cutoff for non-Coulombic (and Coulombic if only 1 arg) (distance units)
    cutoff2 = global cutoff for Coulombic (optional) (distance units)
  {buck/coul/long/cs} args = cutoff (cutoff2)
    cutoff = global cutoff for Buckingham (and Coulombic if only 1 arg) (distance units)
    cutoff2 = global cutoff for Coulombic (optional) (distance units)
  {born/coul/dsf/cs} args = alpha cutoff (cutoff2)
    alpha = damping parameter (inverse distance units)
    cutoff = global cutoff for non-Coulombic (and Coulombic if only 1 arg) (distance units)
    cutoff2 = global cutoff for Coulombic (distance units) :pre

[Examples:]

pair_style born/coul/long/cs 10.0 8.0
pair_coeff 1 1 6.08 0.317 2.340 24.18 11.51 :pre

pair_style buck/coul/long/cs 10.0
pair_style buck/coul/long/cs 10.0 8.0
pair_coeff * * 100.0 1.5 200.0
pair_coeff 1 1 100.0 1.5 200.0 9.0 :pre

pair_style born/coul/dsf/cs 0.1 10.0 12.0
pair_coeff * *   0.0 1.00 0.00 0.00 0.00
pair_coeff 1 1 480.0 0.25 0.00 1.05 0.50 :pre

[Description:]

These pair styles are designed to be used with the adiabatic
core/shell model of "(Mitchell and Finchham)"_#MitchellFinchham2.  See
"Section 6.25"_Section_howto.html#howto_25 of the manual for an
overview of the model as implemented in LAMMPS.

The styles with a {coul/long} term are identical to the "pair_style
born/coul/long"_pair_born.html and "pair_style
buck/coul/long"_pair_buck.html styles, except they correctly treat the
special case where the distance between two charged core and shell
atoms in the same core/shell pair approach r = 0.0.  This needs
special treatment when a long-range solver for Coulombic interactions
is also used, i.e. via the "kspace_style"_kspace_style.html command.

More specifically, the short-range Coulomb interaction between a core
and its shell should be turned off using the
"special_bonds"_special_bonds.html command by setting the 1-2 weight
to 0.0, which works because the core and shell atoms are bonded to
each other.  This induces a long-range correction approximation which
fails at small distances (~< 10e-8). Therefore, the Coulomb term which
is used to calculate the correction factor is extended by a minimal
distance (r_min = 1.0-6) when the interaction between a core/shell
pair is treated, as follows

:c,image(Eqs/pair_cs.jpg)

where C is an energy-conversion constant, Qi and Qj are the charges on
the core and shell, epsilon is the dielectric constant and r_min is the
minimal distance.

The pair style {born/coul/dsf/cs} is identical to the
"pair_style born/coul/dsf"_pair_born.html style, which uses the
the damped shifted force model as in "coul/dsf"_pair_coul.html
to compute the Coulomb contribution. This approach does not require
a long-range solver, thus the only correction is the addition of a
minimal distance to avoid the possible r = 0.0 case for a
core/shell pair.

[Restrictions:]

These pair styles are part of the CORESHELL package.  They are only
enabled if LAMMPS was built with that package.  See the "Making
LAMMPS"_Section_start.html#start_3 section for more info.

[Related commands:]

"pair_coeff"_pair_coeff.html, "pair_style born"_pair_born.html,
"pair_style buck"_pair_buck.html

[Default:] none

:line

:link(MitchellFinchham2)
[(Mitchell and Finchham)] Mitchell, Finchham, J Phys Condensed Matter,
5, 1031-1038 (1993).
