# Cell

From DoSPT

The `cell`

keyword is a **required** keyword in the `input`

file. It takes 3 arguments, respectively the moduli of the 3 lattice vectors of an orthorhombic unit cell, AKA a "rectangular" box. The units are **nm**. At the moment, only such rectangular boxes can be used in a DoSPT calculation.

Support for non-orthogonal unit cells (i.e., a generally triclinic unit cell) via a 9-argument `cell`

keyword may be added in the future but is currently not supported.

### Summary

Required/optional | Type | Accepted values | Default | See also |
---|---|---|---|---|

Required | Float (dimension = 3) | Any 3 positive floats | n/a | Input file, trajectory file |

### Example

cell = 10. 15. 12.

where we have defined a rectangular periodic box with dimensions [math]L_x = 10~\text{nm}[/math], [math]L_y = 15~\text{nm}[/math] and [math]L_z = 12~\text{nm}[/math].