cut command

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.

\begin{aligned} H_{l o n g} & = - \frac{μ_{0} {(μ_{B})}^{2}}{4 π} \sum_{i, j, i \neq j}^{N} \frac{g_{i} g_{j}}{r_{i j}^{3}} (3 ({\vec{e}}_{i j} \cdot {\vec{s}}_{i}) ({\vec{e}}_{i j} \cdot {\vec{s}}_{j}) - {\vec{s}}_{i} \cdot {\vec{s}}_{j}) \\ ω_{i} & = \frac{μ_{0} (μ_{B})^{2}}{4 π ℏ} \sum_{j} \frac{g_{i} g_{j}}{r_{i j}^{3}} (3 ({\vec{e}}_{i j} \cdot {\vec{s}}_{j}) {\vec{e}}_{i j} - {\vec{s}}_{j}) \\ F_{i} & = \frac{3 μ_{0} (μ_{B})^{2}}{4 π} \sum_{j} \frac{g_{i} g_{j}}{r_{i j}^{4}} [(({\vec{s}}_{i} \cdot {\vec{s}}_{j}) - 5 ({\vec{e}}_{i j} \cdot {\vec{s}}_{i}) ({\vec{e}}_{i j} \cdot {\vec{s}}_{j})) {\vec{e}}_{i j} + (({\vec{e}}_{i j} \cdot {\vec{s}}_{i}) {\vec{s}}_{j} + ({\vec{e}}_{i j} \cdot {\vec{s}}_{j}) {\vec{s}}_{i})] \end{aligned}

where ${\vec{s}}_{i}$ and ${\vec{s}}_{j}$ are the spin on two magnetic particles, r is their separation distance, and the vector ${\vec{e}}_{i j} = \frac{r_{i} - r_{j}}{| r_{i} - r_{j} |}$ 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 page for more info.

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

Default

none