A Priori Predictions of Phase Transitions in KCaF₃ and RbCaF₃: Existence of a New Ground State

Authors

J. W. Flocken, University of Nebraska at Omaha, Omaha, Nebraska
R. A. Guenther, University of Nebraska at Omaha, Omaha, Nebraska
John R. Hardy, University of Nebraska - LincolnFollow
L. L. Boyer, Naval Research Laboratory, Washington, D. C.

Date of this Version

4-21-1986

Comments

Published in Phys. Rev. B VOLUME 56, NUMBER 16, 21 April 1986. Copyright © 1986 The American Physical Society. Used by permission.

Abstract

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.