Scientific Illustrations -- Perovskite: Pnma vs. Pbnm vs. pseudo-cubic
Bridgmanite is orthorhombic, space group Pbnm, with a = 4.7754 Å, b = 4.9292 Å and c = 6.8969 Å. Sometimes, a pseudo-cubic lattice is introduced with ac ≈ 3.4 Å to compare the slip systems of bridgmanite with those of cubic perovskites. There is a 45° rotation between the Pbnm and the pseudo-cubic indexing, which is a source of great confusion.
Also note that, in some publications bridgmanite is also indexed as Pnma. Axes are swiched between the Pbnm as Pnma indexing. Don't get it wrong!
Perovskite: Pbnm vs. pseudo-cubic
|Bridgmanite, viewed down  in the Pbnm setting||Bridgmanite with the Pbnm unit cell||Bridgmanite with the pseudo-cubic unit cell||Bridgmanite with the Pbnm and pseudo-cubic unit cells|
Perovskite: Pbnm vs. Pnma
|Bridgmanite, viewed down  in the Pbnm setting||Bridgmanite, viewed down  in the Pnma setting||Bridgmanite, viewed down  in the Pbnm setting||Bridgmanite, viewed down  in the Pnma setting|