A theoretical study of perovskites related to CH3NH3PbX3 (X = F, Cl, Br, I)

The bond dissociation energies of MAPI (CH3NH3PbI3) and related perovskites (with F, Cl, Br instead of I and with bases other than methylamine) have been calculated using a simplified model consisting of a corner of the perovskite (PbX3-) and the methyl ammonium (CH3NH3+) and other protonated bases. The values obtained show that besides the size (related to the tolerance factor), the energy of the interaction should be considered. Using relativistic corrections (ADF), the H-1, C-13, N-15 and Pb-207 absolute shieldings were calculated and transformed into chemical shifts by empirical equations established here. The C-13 and N-15 light nuclei were well reproduced by the corner model but the Pb-207 chemical shifts need a large correction factor owing to the fact that lead in the perovskites is surrounded by six iodine atoms instead of the corner's three atoms.