First-Principles Theoretical Explanation of Incommensurate Behavior in RbZnC₄

Authors

V. Katkanant, University of Nebraska - Lincoln
P. J. Edwardson, University of Nebraska - Lincoln
John R. Hardy, University of Nebraska - LincolnFollow
L. L. Boyer, U. S. Naval Research Laboratory, Washington, D. C.

Date of this Version

10-20-1986

Comments

Published in Phys. Rev. B VOLUME 57, NUMBER 16, 20 October 1986. Copyright © 1986 The American Physical Society. Used by permission.

Abstract

We have carried out an ab initio theoretical study of the potential energy and molecular dynamics of Rb₂ZnCl₄. These calculations demonstrate that the incommensurate transition in this compound is caused by the relaxation of imperfect-hexagonal spirals of highly unstable ZnCl₄^2- ions. This leads to angstrom-size displacements with essentially zero energy change. We argue that such "latent" (or imperfect) symmetry could be the general cause of incommensurate transitions in insulators.