# Cell

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

Summary for cell keyword
cell = 10. 15. 12.

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