We have made an a prior; theoretical study of the potential-energy surfaces for KCaF3 and RbCaF3, and have examined the relative stability of the various lower-symmetry structures generated from the cubic perovskite phase by "rotations" of the CaF6 octahedra. A completely new ground state was discovered which, when included in the sequence of energy levels, allows us to give a full account both qualitatively and, in the case of RbCaF3, quantitatively of the phase transition sequences in both systems.
Flocken, John W.; Guenther, R. A.; Hardy, John R.; and Boyer, L. L., "A Priori Predictions of Phase Transitions in KCaF3 and RbCaF3: Existence of a New Ground State" (1986). Physics Faculty Publications. 22.