"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 lj/expand command :h3
pair_style lj/expand/gpu command :h3

[Syntax:]

pair_style lj/expand cutoff :pre
pair_style lj/expand/gpu cutoff :pre

cutoff = global cutoff for lj/expand interactions (distance units) :ul

[Examples:]

pair_style lj/expand 2.5
pair_coeff * * 1.0 1.0 0.5
pair_coeff 1 1 1.0 1.0 -0.2 2.0 :pre

[Description:]

Style {lj/expand} computes a LJ interaction with a distance shifted by
delta which can be useful when particles are of different sizes, since
it is different that using different sigma values in a standard LJ
formula:

:c,image(Eqs/pair_lj_expand.jpg)

Rc is the cutoff which does not include the delta distance.  I.e. the
actual force cutoff is the sum of cutoff + delta.

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:

epsilon (energy units)
sigma (distance units)
delta (distance units)
cutoff (distance units) :ul

The delta values can be positive or negative.  The last coefficient is
optional.  If not specified, the global LJ cutoff is used.

Style {lj/expand/gpu} is a GPU-enabled version of style {lj/expand}.
See more details below.

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The {lj/expand/gpu} style is identical to the {lj/expand} style,
except that each processor off-loads its pairwise calculations to a 
GPU chip. Depending on the hardware available on your system this can provide a
speed-up.  See the "Running on GPUs"_Section_start.html#2_8 section of
the manual for more details about hardware and software requirements
for using GPUs.

More details about these settings and various possible hardware
configuration are in "this section"_Section_start.html#2_8 of the
manual.

Additional requirements in your input script to run with GPU-enabled styles
are as follows:

The "newton pair"_newton.html setting must be {off} and
"fix gpu"_fix_gpu.html must be used. The fix controls
the essential GPU selection and initialization steps.

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

For atom type pairs I,J and I != J, the epsilon, sigma, and shift
coefficients and cutoff distance for this pair style can be mixed.
Shift is always mixed via an {arithmetic} rule.  The other
coefficients are mixed according to the pair_modify mix value.  The
default mix value is {geometric}.  See the "pair_modify" command for
details.

This pair style supports the "pair_modify"_pair_modify.html shift
option for the energy of the pair interaction.

The "pair_modify"_pair_modify.html table option is not relevant
for this pair style.

This pair style supports the "pair_modify"_pair_modify.html tail
option for adding a long-range tail correction to the energy and
pressure of the pair interaction.

This pair style writes its 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.

This pair style can only be used via the {pair} keyword of the
"run_style respa"_run_style.html command.  It does not support the
{inner}, {middle}, {outer} keywords.

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[Restrictions:]

The {lj/expand/gpu} style is part of the "gpu" package. It is only
enabled if LAMMPS was built with that package.  See the "Making
LAMMPS"_Section_start.html#2_3 section for more info.

[Related commands:]

"pair_coeff"_pair_coeff.html

[Default:] none
