Fig. 5. X-ray pair distribution functions for (a) MASnI3, (b) FASnI3, (c) MAPbI3, and (d) FAPbI3 at 360 K of the nearest B–I correlation. (e) Refined displacements of the B-site cation in space group R3m as a function of the temperature indicate large displacements for Sn2+ iodides and minimal displacements for Pb2+ iodides. Refined displacements for the APbBr3 analogs indicate moderate off-centering. Reported Sn2+ displacements in CsSnBr3 are overlaid for comparison.29 The dashed lines in (a–d) indicate the distinct bond lengths extracted from modeling the local structure in the space group R3m ([111] displacement).
