Fig. 3: Candidate binary oxides under strain.
From: Phase stability of entropy stabilized oxides with the α-PbO2 structure
Energy difference as a function of fixed unit cell volume for the seven d0 and d10 tetravalent binary oxides a GeO2, b TiO2, c SnO2, d HfO2, e ZrO2, f PbO2, and g CeO2 in the four candidate crystal structures (fluorite, rutile, baddeleyite, and α-PbO2). The energy difference ΔEtrans+strain represents the transformation energy and the strain energy relative to the ground state structure and volume. The cation size is the determining factor both for which crystal structure is most stable (six-, seven-, or eight-fold coordinated) and for which crystal volume the oxide is the most stable. The α-PbO2 structure is consistently among the lowest energy structure for all cations and has a relatively flat energy distribution at its minimum, suggesting it can accommodate a larger distribution in cation sizes.
