Energy Jahn-Teller

The ground state behaviour observed for Jahn-Teller impurities in cubic lattices has often been explained a posteriori by fitting experimental data to quantities like the average random strains, the Jahn-Teller energy, E]T, or the % frequency [5]. In particular when EJT/iuov < 1 the observation at low temperatures of a cubic angular pattern is favoured, while if E /Hcoe > 1 a static EPR spectrum is expected [1-3]. 

The Jahn-Teller energy Ejt, Fig. 1(A), should be available from optical spectroscopy261, as Ejt should be in the order of 1500-2500 cm 1, but should not be significantly temperature variable161. 

Example of Estimations of the Jahn-Teller Energy from the Second Order Ham Effect... 

The occurrence of two types of CO states can be understood qualitatively in terms of the variation of the exchange couplings, Jfu 4nd nd the single-ion Jahn-Teller energy... 

Future applications of the AOM will include the analysis of the optical spectra and magnetic properties of transition metal ions located in polynuclear systems. Calculations on infinite structures (chains) have already been reported [110], and a parametrization scheme for the evaluation of orbital-exchange parameters in magnetically coupled dinuclear complexes was presented recently [111]. Another interesting aspect concerns the dynamic extension of the AOM which allows, for example, Jahn-Teller energies to be calculated [112, 113]. Finally, it should be... 

G. D. Bent, G. F. Adams, R. J. Bartlett, and G. D. Purvis, Many-body perturbation theory electronic structure calculations for the methoxy radical. I. Determination of Jahn-Teller energy surfaces, spin-orbit splitting, and Zeeman effect, manuscript submitted. 

The stoi7 begins with studies of the molecular Jahn-Teller effect in the late 1950s [1-3]. The Jahn-Teller theorems themselves [4,5] are 20 years older and static Jahn-Teller distortions of elecbonically degenerate species were well known and understood. Geomebic phase is, however, a dynamic phenomenon, associated with nuclear motions in the vicinity of a so-called conical intersection between potential energy surfaces. 

It was shown by several workers that in this case the first-order Jahn-Teller distortion is due to an ej vibration, and that the second-order distortion vanishes. Therefore, in terms of simple Jahn-Teller theoi, the moat around the symmetric point should be a Mexican hat type, without secondary minima. This expectation was borne out by high-level quantum chemical calculations, which showed that the energy difference between the two expected C2v structures ( A2 and Bi) were indeed very small [73]. 

H3 (and its isotopomers) and the alkali metal triiners (denoted generally for the homonuclears by X3, where X is an atom) are typical Jahn-Teller systems where the two lowest adiabatic potential energy surfaces conically intersect. Since such manifolds of electronic states have recently been discussed [60] in some detail, we review in this section only the diabatic representation of such surfaces and their major topographical details. The relevant 2x2 diabatic potential matrix W assumes the fomi... 

Now, we examine the effect of vibronic interactions on the two adiabatic potential energy surfaces of nonlinear molecules that belong to a degenerate electronic state, so-called static Jahn-Teller effect. 

Clearly, Eq. (E.12) shows that to a first approximation the elecbonic energy varies linearly with displacements in p, increasing for one component state while decreasing for the other. Thus, the potential minimum cannot be at p = 0. This is the statement of the Jahn-Teller theorem for a X3 molecule belonging to the D3 , point gioup. 

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