# pair_style spin/dipole/long command

## Syntax

pair_style spin/dipole/cut cutoff
pair_style spin/dipole/long cutoff

• cutoff = global cutoff for magnetic dipole energy and forces (optional) (distance units)

## Examples

pair_style spin/dipole/cut 10.0
pair_coeff * * 10.0
pair_coeff 2 3 8.0

pair_style spin/dipole/long 9.0
pair_coeff * * 10.0
pair_coeff 2 3 6.0

## Description

Style spin/dipole/cut computes a short-range dipole-dipole interaction between pairs of magnetic particles that each have a magnetic spin. The magnetic dipole-dipole interactions are computed by the following formulas for the magnetic energy, magnetic precession vector omega and mechanical force between particles I and J.

where si and sj are the spin on two magnetic particles, r is their separation distance, and the vector e = (Ri - Rj)/|Ri - Rj| is the direction vector between the two particles.

Style spin/dipole/long computes long-range magnetic dipole-dipole interaction. A kspace_style must be defined to use this pair style. Currently, kspace_style ewald/dipole/spin and kspace_style pppm/dipole/spin support long-range magnetic dipole-dipole interactions.

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

This pair style does not support the pair_modify tail option for adding long-range tail corrections to energy and pressure.

This pair style writes its information to binary restart files, so pair_style and pair_coeff commands do not need to be specified in an input script that reads a restart file.

## Restrictions

The spin/dipole/cut and spin/dipole/long styles are part of the SPIN package. They are only enabled if LAMMPS was built with that package. See the Build package doc page for more info.

Using dipole/spin pair styles with electron units is not currently supported.