### Syntax

`aList = sw_extendlattice(nExt,aList)`

`[aList, SSext] = sw_extendlattice(nExt,aList,SS)`

### Description

`aList = sw_extendlattice(nExt,aList)`

creates a superlattice
and calculates all atomic positions within the new superlattice by
tiling it with the original cell.

`[aList, SSext] = sw_extendlattice(nExt,aList,SS)`

also calculates the
bond matrix for the supercell by properly including all internal bonds
and bonds between atoms in different supercells.

### Input Arguments

`nExt`

- Size of the supercell in units of the original cell in a row vector with 3 elements.
`aList`

- List of the atoms, produced by spinw.matom.
`SS`

- Interactions matrices in the unit cell. Struct where each field contains an interaction matrix.

### Output Arguments

`aList`

- Parameters of the magnetic atoms in a struct with the following fields:
`RRext`

Positions of magnetic atoms in lattice units of the supercell stored in a matrix with dimensions of \([3\times n_{magExt}]\).`Sext`

Spin length of the magnetic atoms in a row vector with \(n_{magExt}\) number of elements.

`SSext`

- Interaction matrix in the extended unit cell, struct type.
In the struct every field is a matrix. Every column of the
matrices describes a single bond, the following fields are generally
defined:
`iso`

Isotropic exchange interactions.`ani`

Anisotropic exchange interations.`dm`

Dzyaloshinsky-Moriya interaction terms.`gen`

General \([3\times 3]\) matrix contains the exchange interaction.