(I use [VESTA][1] to visualize supercells with the `VASP` `POSCAR` format.) Consider the following cell which has haunted me: POSCAR 3.5668661195641991 1.00000000 -1.00000000 -1.00000000 1.00000000 1.00000000 -1.00000000 1.50000000 0.00000000 2.50000000 A B 8 24 Direct 1.00000000 1.00000000 1.00000000 0.06250000 0.06250000 0.25000000 0.65625000 0.15625000 0.12500000 0.71875000 0.21875000 0.37500000 0.81250000 0.81250000 0.25000000 0.15625000 0.65625000 0.12500000 0.21875000 0.71875000 0.37500000 0.93750000 0.93750000 0.75000000 0.12500000 0.12500000 0.50000000 0.53125000 0.03125000 0.62500000 0.18750000 0.18750000 0.75000000 0.59375000 0.09375000 0.87500000 0.25000000 0.25000000 1.00000000 0.31250000 0.31250000 0.25000000 0.37500000 0.37500000 0.50000000 0.03125000 0.53125000 0.62500000 0.78125000 0.28125000 0.62500000 0.43750000 0.43750000 0.75000000 0.09375000 0.59375000 0.87500000 0.84375000 0.34375000 0.87500000 0.90625000 0.40625000 0.12500000 0.56250000 0.56250000 0.25000000 0.96875000 0.46875000 0.37500000 0.62500000 0.62500000 0.50000000 0.28125000 0.78125000 0.62500000 0.68750000 0.68750000 0.75000000 0.34375000 0.84375000 0.87500000 0.75000000 0.75000000 1.00000000 0.40625000 0.90625000 0.12500000 0.50000000 0.50000000 1.00000000 0.46875000 0.96875000 0.37500000 0.87500000 0.87500000 0.50000000 I wish to rotate (or transform) this cell so that its non-orthogonal lattice vectors become orthogonal. I'm not sure anymore if this can be done. Required lattice vectors: a` = 1.0 -1.0 0.0 b` = 1.0 1.0 -2.5 c` = 2.5 2.5 2.0 Original intent: This is a random FCC solid solution (SQS). I want to change the cell so that it looks like a usual FCC supercell. [1]: https://jp-minerals.org/vesta/en/download.html