Illustrations scientifiques -- Perovskite: Pnma vs. Pbnm vs. pseudo-cubique

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-cubique

Bridgmanite, vue depuis [001] dans l'indexation Pbnm	Bridgmanite avec la maille Pbnm	Bridgmanite avec la maille pseudo-cubique	Bridgmanite avec les mailles Pbnm et pseudo-cubique

Perovskite: Pbnm vs. Pnma

Bridgmanite, vue depuis [010] dans l'indexation Pbnm	Bridgmanite, vue depuis [100] dans l'indexation Pnma	Bridgmanite, vue depuis [100] dans l'indexation Pbnm	Bridgmanite, vue depuis [001] dans l'indexation Pnma