DFT predicted relative energies between the experimental post-perovskite phase (CsM(NCS)3 = pPv) and the two known AM(NCS)3 perovskite structure-types: CsCd(NCS)3 = Cs[Cd]; (NH4)2NiCd(NCS)6 = NH4[NiCd]. The perovskite structures were generated by swapping the A site cation for Cs+ and the B site cation(s) by the appropriate transition metal.
(meV per formula unit).