lammps/doc/pair_nm.txt

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:line

pair_style nm command :h3
pair_style nm/cut/coul/cut command :h3
pair_style nm/cut/coul/long command :h3

[Syntax:]

pair_style style args :pre 

style = {nm} or {nm/cut/coul/cut} or {nm/cut/coul/long} :ulb,l
args = list of arguments for a particular style :l
  {nm} args = cutoff
    cutoff = global cutoff for Pair interactions (distance units)
  {nm/cut/coul/cut} args = cutoff (cutoff2)
    cutoff = global cutoff for Pair (and Coulombic if only 1 arg) (distance units)
    cutoff2 = global cutoff for Coulombic (optional) (distance units)
  {nm/cut/coul/long} args = cutoff (cutoff2)
    cutoff = global cutoff for Pair (and Coulombic if only 1 arg) (distance units)
    cutoff2 = global cutoff for Coulombic (optional) (distance units) :pre
:ule

[Examples:]

pair_style nm 12.0
pair_coeff * * 0.01 5.4 8.0 7.0
pair_coeff 1 1 0.01 4.4 7.0 6.0 :pre

pair_style nm/cut/coul/cut 12.0 15.0
pair_coeff * * 0.01 5.4 8.0 7.0
pair_coeff 1 1 0.01 4.4 7.0 6.0 :pre

pair_style nm/cut/coul/long 12.0 15.0
pair_coeff * * 0.01 5.4 8.0 7.0
pair_coeff 1 1 0.01 4.4 7.0 6.0 :pre

[Description:]

Style {nm} computes site-site interactions based on the N-M potential
by "Clarke"_#Clarke, mainly used for ionic liquids.  A site can
represent a single atom or a united-atom site.  The energy of an
interaction has the following form:

:c,image(Eqs/pair_nm.jpg)

Rc is the cutoff.

Style {nm/cut/coul/cut} adds a Coulombic pairwise interaction given by

:c,image(Eqs/pair_coulomb.jpg)

where C is an energy-conversion constant, Qi and Qj are the charges on
the 2 atoms, and epsilon is the dielectric constant which can be set 
by the "dielectric"_dielectric.html command.  If one cutoff is
specified in the pair_style command, it is used for both the NM and 
Coulombic terms.  If two cutoffs are specified, they are used as
cutoffs for the NM and Coulombic terms respectively.

Styles {nm/cut/coul/long} compute the same
Coulombic interactions as style {nm/cut/coul/cut} except that 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.

For all of the {nm} pair styles, 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.

E0 (energy units)
r0 (distance units)
n (unitless)
m (unitless)
cutoff1 (distance units)
cutoff2 (distance units) :ul

The latter 2 coefficients are optional.  If not specified, the global
NM and Coulombic cutoffs specified in the pair_style command are used.
If only one cutoff is specified, it is used as the cutoff for both NM
and Coulombic interactions for this type pair.  If both coefficients
are specified, they are used as the NM and Coulombic cutoffs for this
type pair.  You cannot specify 2 cutoffs for style {nm}, since it
has no Coulombic terms.

For {nm/cut/coul/long} only the NM cutoff can be specified since a
Coulombic cutoff cannot 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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[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.

All of the {nm} pair styles supports the
"pair_modify"_pair_modify.html shift option for the energy of the pair
interaction.

The {nm/cut/coul/long} pair styles support the
"pair_modify"_pair_modify.html table option since they can tabulate
the short-range portion of the long-range Coulombic interaction.

All of the {nm} pair styles support the "pair_modify"_pair_modify.html
tail option for adding a long-range tail correction to the energy and
pressure for the NM portion of the pair interaction.

All of the {nm} pair styles write their information to "binary restart
files"_restart.html, so pair_style and pair_coeff commands do not need
to be specified in an input script that reads a restart file.

All of the {nm} pair 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.

[Restrictions:]

These pair styles are part of the MISC package.  It is 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

[Default:] none

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:link(Clarke)
[(Clarke)] Clarke and Smith, J Chem Phys, 84, 2290 (1986).