Coupling Jahn-Teller

Figure 1. Adiabatic potential surfaces (a) for the linear E x e case and (b) for a state with linear Jahn-Teller coupling and spin-orbit coupling to a state,...

Warren KD (1984) Calculations of the Jahn-Teller Coupling Constants for d Systems in Octahedral Symmetry via the Angular Overlap Model. 57 119-145 Warren KD (1977) Ligand Field Theory off-Orbital Sandwich Complexes. 33 97-137 Warren KD (1976) Ligand Field Theory of Metal Sandwich Complexes. 27 45-159 Watson RE, Perlman ML (1975) X-Ray Photoelectron Spectroscopy. Application to Metals and Alloys. 24 83-132... 

Various other interactions have been considered as the driving force for spin-state transitions such as the Jahn-Teller coupling between the d electrons and a local distortion [73], the coupling between the metal ion and an intramolecular distortion [74, 75, 76] or the coupling between the d electrons and the lattice strain [77, 78]. At present, based on the available experimental evidence, the contribution of these interactions cannot be definitely assessed. Moreover, all these models are mathematically rather ambitious and do not show the intuitively simple structure inherent in the effect of a variation of molecular volume considered here. Their discussion has to be deferred to a more specialized study. 

Warren, K. D. Calculations of the Jahn-Teller Coupling Constants for d Systems in Octahedral Symmetry via the Angular Overlap Model. Vol. 57, pp. 119-145. 

Kambara presented a ligand field theoretical model for SCO in transition metal compounds which is based on the Jahn-Teller coupling between the d-electrons and local distortion as the driving force for a spin transition [193]. The author applied this model also to interpret the effect of pressure on the ST behaviour in systems with gradual and abrupt transitions [194]. By considering the local molecular distortions dynamically this model turned out to be suited to account for cooperative interactions during the spin transition [195]. 

Kambara (1979) has proposed a microscopic model in which the coupling between the d-electrons and the lattice has been given a definitive meaning. Assuming that there is Jahn-Teller coupling between the d-electrons and the local intramolecular distortion, the Hamiltonian of the system is written as... 

Fig. 13. Top Schematic representation of the two components of the Jahn-Teller-active vibrational mode for the E e Jahn-Teller coupling problem for octahedral d9 Cu(II) complexes. Bottom Resulting first-order Mexican hat potential energy surface for showing the Jahn-Teller radius, p, and the first-order Jahn-Teller stabilization energy, Ejt.

Fig. 16. The absorption spectrum of Sn2 + in crystalline KC1 at 77°K reproduced from ref. 108. The splitting of the band is attributed to Jahn-Teller coupling in a Tlu excited state (see ref. 123).

Johnson and Messmer expanded the interpretation of the bonding overlap integral to a Jahn-Teller coupling parameter fi via the relation Sbond(EF) (m/My, where m, M are the electron and nuclear masses, respectively. According to this expression, there are two derived trends (1) for physically realistic values of d (d > 0.05 nm), Tc drops as d increases and (2) at constant d, Tc increases as S increases. 

Here the constant b was assumed to have the same value for both the E and E states. This assumption is consistent with transition [2] being a narrow peak while transitions [3] and [4] are broader bands, as the structure of the near-infrared absorption of CuIJY demonstrates (Fig. 9). Transitions [2], [3], and [4] are assigned the observed frequencies 10900, 12700, and 14650 cm l, and transition [1] will be shown to be below 1000 cm-l. The energy difference between transitions [2] and [3] depends only on the Jahn-Teller coupling constant, which is determined to be b = 3600 cm- from the observed frequencies. The spin-orbit coupling constant X is equal to 829 cm l for the free Cu11 ion (23), but in Cu11 complexes assumes the value close to 400 cm l. In the present analysis the band centers are insensitive tj various choices of,X. With X = 400 cm and b2 = 3600 cm, the... 

Tunneling splitting in a two-level system with pseudo-Jahn-Teller coupling 66... 

TUNNELING SPLITTING IN A TWO-LEVEL SYSTEM WITH PSEUDO-JAHN-TELLER COUPLING... 

A parameterization method of the Hamiltonian for two electronic states which couple via nuclear distortions (vibronic coupling), based on density functional theory (DFT) and Slaters transition state method, is presented and applied to the pseudo-Jahn-Teller coupling problem in molecules with an s2-lone pair. The diagonal and off-diagonal energies of the 2X2 Hamiltonian matrix have been calculated as a function of the symmetry breaking angular distortion modes and r (Td)] of molecules with the coordination number CN = 3... 

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