On the tetragonal distortion of octahedral systems in an E_gelectronic state

Abstract

The tetragonal distortion of octahedral (ML6) systems having two-fold orbital degeneracy is discussed on a model which takes into account covaleney and the essential features of the Jahn-Teller effects. Theoretically both elongation and compression along the tetragonal axis are possible, depending on the sign of the coefficients involved in the first and the second-order terms. Covalency effects seem to influence this fact.A qualitative discussion of these results is presented.

First-principles investigation of the cooperative Jahn-Teller effect for octahedrally coordinated transition-metal ions

“…24 A later paper by Pryce et al discusses both higher-order elastic and vibronic terms. 25 First, they point out that the third-order elastic term would support a positive Q 3 distortion in any reasonable potential model, due to the fact that the two M -O bonds are contracted twice as much as the other four. Second, they reason that when the covalency is small, the second-order vibronic coupling may be negative or positive by a small difference, and that it would increase with increasing covalency.…”

A MO calculation of the static Jahn-Teller effect in CuF6-4

“…It is natural to suppose that this sign is dependent upon the chosen wavefunctions. It is, therefore, gratifying that very recently Pryce, Sinha and Tanabe [3], without performing numerical calculations, have come to the conclusion that the amount of ' covalency' in the wavefunctions influences this sign. A similar conclusion was also reached by Ballhausen and de Heer [4] in their calculations of VCI~.…”