r0

20r

r+

r-

Need to account for all the distances, these go into the Madelung constant

ZnS Rutile - TiO2

CaF2

Perovskite ABX3

Spinel – MgAl2O4, Fe3O4

Contains octahedra and tetrahedra, but the repeat pattern is simple

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In situ temperature-dependent synchrotron XRD patterns of black CsSnI3 on heating. Changes in the

Bragg reflection peaks indicate temperature-driven phase transitions to higher symmetry on heating:

orthorhombic (B-γ) to tetragonal (B-β) above 362.1 ± 5.4 K and the latter to orthorhombic (B-α) above

440.5 ± 3.5 K. The representative XRD peaks that reflect phase transitions are indexed.

Hexagonal non-perovskite FAPbI3 converted into a trigonal perovskite phase