# pair_style kim command

## Syntax

pair_style kim model


model = name of KIM model (potential)

## Examples

pair_style kim ex_model_Ar_P_LJ
pair_coeff * * Ar Ar


## Description

This pair style is a wrapper on the Knowledge Base for Interatomic Models (OpenKIM) repository of interatomic potentials, so that they can be used by LAMMPS scripts.

Note that in LAMMPS lingo, a KIM model driver is a pair style (e.g. EAM or Tersoff). A KIM model is a pair style for a particular element or alloy and set of parameters, e.g. EAM for Cu with a specific EAM potential file.

See the current list of KIM model drivers.

See the current list of all KIM models

To use this pair style, you must first download and install the KIM API library from the OpenKIM website. The KIM section of the Packages details doc page has instructions on how to do this with a simple make command, when building LAMMPS.

See the examples/kim dir for an input script that uses a KIM model (potential) for Lennard-Jones.

The argument model is the name of the KIM model for a specific potential as KIM defines it. In principle, LAMMPS can invoke any KIM model. You should get an error or warning message from either LAMMPS or KIM if there is an incompatibility.

Only a single pair_coeff command is used with the kim style which specifies the mapping of LAMMPS atom types to KIM elements. This is done by specifying N additional arguments after the * * in the pair_coeff command, where N is the number of LAMMPS atom types:

• N element names = mapping of KIM elements to atom types

As an example, imagine the KIM model supports Si and C atoms. If your LAMMPS simulation has 4 atom types and you want the 1st 3 to be Si, and the 4th to be C, you would use the following pair_coeff command:

pair_coeff * * Si Si Si C


The 1st 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 Si as defined within KIM. The final C argument maps LAMMPS atom type 4 to C as defined within KIM.

In addition to the usual LAMMPS error messages, the KIM library itself may generate errors, which should be printed to the screen. In this case it is also useful to check the kim.log file for additional error information. The file kim.log should be generated in the same directory where LAMMPS is running.

To download, build, and install the KIM library on your system, see the lib/kim/README file. Once you have done this and built LAMMPS with the KIM package installed you can run the example input scripts in examples/kim.

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

This pair style does not support the pair_modify mix, shift, table, and tail options.

This pair style does not write its information to binary restart files, since KIM stores the potential parameters. 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 command. It does not support the inner, middle, outer keywords.

## Restrictions

This pair style is part of the KIM package. It is only enabled if LAMMPS was built with that package. See the Build package doc page for more info.

This current version of pair_style kim is compatible with the kim-api package version 2.0.0 and higher.