lammps/doc/pair_born.txt

"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)

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pair_style born command :h3
pair_style born/omp command :h3
pair_style born/coul/long command :h3
pair_style born/coul/long/cuda command :h3
pair_style born/coul/long/omp command :h3
pair_style born/coul/wolf command :h3

[Syntax:]

pair_style style args :pre

style = {born} or {born/coul/long}
args = list of arguments for a particular style :ul
  {born} args = cutoff
    cutoff = global cutoff for non-Coulombic interactions (distance units)
  {born/coul/long} 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)
  {born/coul/wolf} 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 (optional) (distance units) :pre

[Examples:]

pair_style born 10.0
pair_coeff * * 6.08 0.317 2.340 24.18 11.51
pair_coeff 1 1 6.08 0.317 2.340 24.18 11.51 :pre

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

pair_style born/coul/wolf 0.25 10.0
pair_style born/coul/wolf 0.25 10.0 9.0
pair_coeff * * 6.08 0.317 2.340 24.18 11.51
pair_coeff 1 1 6.08 0.317 2.340 24.18 11.51 :pre

[Description:]

The {born} style computes the Born-Mayer-Huggins or Tosi/Fumi
potential described in "(Fumi and Tosi)"_#FumiTosi, given by

:c,image(Eqs/pair_born.jpg)

where sigma is an interaction-dependent length parameter, rho is an
ionic-pair dependent length parameter, and Rc is the cutoff.

The {born/coul/long} style adds a Coulombic term as described for the
"coul/long"_pair_coul.html pair style.  An additional damping factor
is applied to the Coulombic term so it can be used in conjunction with
the "kspace_style"_kspace_style.html command and its {ewald} or {pppm}
option.  The Coulombic cutoff specified for this style means that
pairwise interactions within this distance are computed directly;
interactions outside that distance are computed in reciprocal space.

If one cutoff is specified for the {born/coul/long} style, it is used
for both the A,C,D and Coulombic terms.  If two cutoffs are specified,
the first is used as the cutoff for the A,C,D terms, and the second is
the cutoff for the Coulombic term.

The {born/coul/wolf} style adds a Coulombic term as described for the
Wolf potential in the "coul/wolf"_pair_coul.html pair style.

If one cutoff is specified for the {born/coulk/long} style, it is used
for both the A,C,D and Coulombic terms.  If two cutoffs are specified,
the first is used as the cutoff for the A,C,D terms, and the second is
the cutoff for the Coulombic term.

Note that these potentials are related to the "Buckingham
potential"_pair_born.html.

The following coefficients must be defined for each pair of atoms
types via the "pair_coeff"_pair_coeff.html command as in the examples
above, or in the data file or restart files read by the
"read_data"_read_data.html or "read_restart"_read_restart.html
commands, or by mixing as described below:

A (energy units)
rho (distance units)
sigma (distance units)
C (energy units * distance units^6)
D (energy units * distance units^8)
cutoff (distance units) :ul

The second coefficient, rho, must be greater than zero.

The last coefficient is optional.  If not specified, the global A,C,D
cutoff specified in the pair_style command is used.

For {buck/coul/long} and {born/coul/wolf} no Coulombic cutoff can be
specified for an individual I,J type pair.  All type pairs use the
same global Coulombic cutoff specified in the pair_style command.

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Styles with a {cuda}, {gpu}, {omp}, or {opt} suffix are functionally 
the same as the corresponding style without the suffix.  They have 
been optimized to run faster, depending on your available hardware, 
as discussed in "this section"_Section_accelerate.html of the manual.
The accelerated styles take the same arguments and should produce the
same results, except for round-off and precision issues.

These accelerated styles are part of the USER-CUDA, GPU, USER-OMP and OPT
packages, respectively.  They are only enabled if LAMMPS was built with
those packages.  See the "Making LAMMPS"_Section_start.html#start_3
section for more info.

You can specify the accelerated styles explicitly in your input script
by including their suffix, or you can use the "-suffix command-line
switch"_Section_start.html#start_6 when you invoke LAMMPS, or you can
use the "suffix"_suffix.html command in your input script.

See "this section"_Section_accelerate.html of the manual for more
instructions on how to use the accelerated styles effectively.

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[Mixing, shift, table, tail correction, restart, rRESPA info]:

These pair styles do not support mixing.  Thus, coefficients for all
I,J pairs must be specified explicitly.

These styles support the "pair_modify"_pair_modify.html shift option
for the energy of the exp(), 1/r^6, and 1/r^8 portion of the pair
interaction.

The {born/coul/long} pair style does not support the
"pair_modify"_pair_modify.html table option since a tabulation
capability has not yet been added to this potential.

These styles support the pair_modify tail option for adding long-range
tail corrections to energy and pressure.

Thess styles writes thei information to binary "restart"_restart.html
files, so pair_style and pair_coeff commands do not need to be
specified in an input script that reads a restart file.

These styles can only be used via the {pair} keyword of the "run_style
respa"_run_style.html command.  They do not support the {inner},
{middle}, {outer} keywords.

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[Restrictions:]

The {born/coul/long} style is part of the KSPACE package.  It is only
enabled if LAMMPS was built with that package (which it is by
default).  See the "Making LAMMPS"_Section_start.html#start_3 section
for more info.

[Related commands:]

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

[Default:] none

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:link(FumiTosi)
Fumi and Tosi, J Phys Chem Solids, 25, 31 (1964),
Fumi and Tosi, J Phys Chem Solids, 25, 45 (1964).