Jahn-Teller effect distortion origin

It seems natural to suppose that the tetragonal distortion of the tri-anion results from the Jahn-Teller effect. In order to study the problem more thoroughly we undertook recently the DFT calculations of this cluster as well as of several other hexanuclear rhenium chalcohalide clusters. The technical details of these calculations can be found in the original publication [8]. Here we only want to note that the introduction of relativistic corrections for Re atoms is crucial for the correct reproduction of the geometry of clusters. In our calculations, this was done by the zero order regular approximation (ZORA) Hamiltonian [9] within ADF 2000.02 package [10]. 

Somewhat paradoxically, symmetry is seen to play an important role in the understanding of the Jahn-Teller effect, the very nature of which is symmetry destruction [52], In a recent review the original paper published by Jahn and Teller [53] was called one of the most seminal papers in chemical physics [54], Only a brief discussion of this effect will be given here for more detail we refer the reader to References [55-59], Bersuker says that all structural instabilities and distortions of high-symmetry configurations of polyatomic systems are of Jahn-Teller origin (here he also refers to other related effects, such as the Renner-Teller effect and the pseudo-Jahn-Teller effect—they will be mentioned later). Bersuker likes to call this the... 

During the last decade it has been observed that the excited state of optical centers is often strongly distorted due to the Jahn-Teller effect. This puts the simple configurational coordinate model with the breathing mode as a coordinate in severe doubt. Also, it now becomes clear that the Stokes shift is in many cases due to a relaxation via a Jahn-Teller active mode. Let us illustrate these statements by several examples that originate from three types of centers, viz., transition... 

Fig. 9.10. The Peierls effect has the same origin as the Jahn-Teller effect in removing the electronic level degeneracy by distorting the tem Jahn, E. Teller, Proc. Roy. Soc. A161 (1937) 220). (a) The electrons occupy half the FEZ, i.e. a standing for the nearest-neighbour dis-...

The Jahn-Teller (JT) effect occurs in the presence of degenerate electronic states. A spontaneous distortion of the lattice (or here of the C60 molecule) would lift the degeneracy between these states, if it reduces the symmetry at the origin of the degeneracy. If these levels are only partially occupied, the electrons occupy the... 

---