Structurally unstable AIII BiO3 perovskites are predicted to be topological insulators but their stable structural forms are trivial band insulators

The quest for broadening the materials base of topological insulators (TIs) beyond the handful of presently known examples has recently led to exploratory calculations of the topological Z2 metric from the band structure of various candidate compounds in assumed crystal structures. However, structural transformations such as volume compression, lattice straining, or atom swaps that are used to instigate in a trivial insulator the band inversion underlying TI-ness, might also destabilize the system to the point that it either distorts into a more stable structure or does not form at all. Whether the more stable form of the candidate material is a TI, it is to be determined. Yet, often TI discovery calculations do not assess whether the postulated structural forms predicted to be TIs are also the stable forms of these compounds. Here, we show that in the broad family of III-Bi-O3 oxides (III=Al, Ga, In, Sc, Y, and La), the cubic AIIIBiO3 perovskite structure, which has been recently predicted to be TI for YBiO3, is unstable, whereas the stable AIIIBiO3 structural forms are trivial band insulators.