The Jahn-Teller effect in chemistry

Abstract

A uniform view of electronic degeneracies, resulting from finite point group symmetries, is developed. It relates any n-fold degeneracy to the geometrical structure formed by the set of equidistant points in a space with exactly n dimensions. Jahn-Teller interactions within the degenerate manifold can simply be represented as bond stretchings of this structure. This approach thus can be qualified as the "chemical perspective" to the study of vibronic instabilities. The procedure is described for two-fold, three-fold, four-fold, and five-fold degeneracies. As a result a simple general proof of the Jahn-Teller theorem can be obtained. The electronic degeneracy is connected to the reaction graph of the stable minima on the surrounding Jahn-Teller surface. The findings are illustrated with some structural and dynamic molecular examples. © 2007 The Chemical Society of Japan.