# pair_style gw command

# pair_style gw/zbl command

## Syntax

``` LAMMPS
pair_style style
```

-   style = *gw* or *gw/zbl*

## Examples

``` LAMMPS
pair_style gw
pair_coeff * * SiC.gw Si C C

pair_style gw/zbl
pair_coeff * * SiC.gw.zbl C Si
```

## Description

The *gw* style computes a 3-body [Gao-Weber](Gao) potential; similarly
*gw/zbl* combines this potential with a modified repulsive ZBL core
function in a similar fashion as implemented in the
[tersoff/zbl](pair_tersoff_zbl) pair style.

Unfortunately the author of this contributed code has not been able to
submit a suitable documentation explaining the details of the
potentials. The LAMMPS developers thus have finally decided to release
the code anyway with only the technical explanations. For details of the
model and the parameters, please refer to the linked publication.

Only a single pair_coeff command is used with the *gw* and *gw/zbl*
styles which specifies a Gao-Weber potential file with parameters for
all needed elements. These are mapped to LAMMPS atom types by specifying
N additional arguments after the filename in the pair_coeff command,
where N is the number of LAMMPS atom types:

-   filename
-   N element names = mapping of GW elements to atom types

See the [pair_coeff](pair_coeff) page for alternate ways to specify the
path for the potential file.

As an example, imagine a file SiC.gw has Gao-Weber values for Si and C.
If your LAMMPS simulation has 4 atoms types and you want the first 3 to
be Si, and the fourth to be C, you would use the following pair_coeff
command:

``` LAMMPS
pair_coeff * * SiC.gw Si Si Si C
```

The first 2 arguments must be \* \* so as to span all LAMMPS atom types.
The first three Si arguments map LAMMPS atom types 1,2,3 to the Si
element in the GW file. The final C argument maps LAMMPS atom type 4 to
the C element in the GW file. If a mapping value is specified as NULL,
the mapping is not performed. This can be used when a *gw* potential is
used as part of the *hybrid* pair style. The NULL values are
placeholders for atom types that will be used with other potentials.

Gao-Weber files in the *potentials* directory of the LAMMPS distribution
have a \".gw\" suffix. Gao-Weber with ZBL files have a \".gz.zbl\"
suffix. The structure of the potential files is similar to other
many-body potentials supported by LAMMPS. You have to refer to the
comments in the files and the literature to learn more details.

------------------------------------------------------------------------

## Mixing, shift, table, tail correction, restart, rRESPA info

For atom type pairs I,J and I != J, where types I and J correspond to
two different element types, mixing is performed by LAMMPS as described
above from values in the potential file.

This pair style does not support the [pair_modify](pair_modify) shift,
table, and tail options.

This pair style does not write its information to [binary restart
files](restart), since it is stored in potential files. Thus, you need
to re-specify the pair_style and pair_coeff commands 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) command. It does not support the *inner*,
*middle*, *outer* keywords.

------------------------------------------------------------------------

## Restrictions

This pair style is part of the MANYBODY package. It is only enabled if
LAMMPS was built with that package. See the [Build
package](Build_package) page for more info.

This pair style requires the [newton](newton) setting to be \"on\" for
pair interactions.

The Gao-Weber potential files provided with LAMMPS (see the potentials
directory) are parameterized for metal [units](units). You can use the
GW potential with any LAMMPS units, but you would need to create your
own GW potential file with coefficients listed in the appropriate units
if your simulation does not use \"metal\" units.

## Related commands

[pair_coeff](pair_coeff)

## Default

none

------------------------------------------------------------------------

::: {#Gao}
**(Gao)** Gao and Weber, Nuclear Instruments and Methods in Physics
Research B 191 (2012) 504.
:::