Fig. 3

Structural effects on the bandstructure of MAPbI₃. Comparisons between the bandstructures of fully relaxed (blue) and MA-relaxed (red) MAPbI₃ structures. In a, b, the bandstructures are shown for single-formula-unit cubic structures with the MA ions aligned in the [100] direction, computed within the LDA (a) and HSE (b) approximations of DFT. c Bandstructures for a 4-formula-unit tetragonal supercell. The Rashba splitting, which is magnified in the right panel insets, is in all cases much greater in the fully relaxed structures due to the large PbI framework distortions that break inversion symmetry. The k-path labeling of the tetragonal cell is taken from the ref. ⁶⁵