Other Jahn-Teller systems explored through DFT

OTHER JAHN-TELLER SYSTEMS EXPLORED THROUGH DFT 4.1. Cu2+ doped cubic oxides 

Therefore, this value of V found for MgO Cu2+ is practically the same as that obtained for NaCl Rh2+. The big difference between K = 4.5 eV/A2 for NaCl Rh2+ and K = 14 eV/A2 for MgO Cu2+ is thus the main responsible for the small values of oq = — 0.023 A and En = 0.035 eV found in the latter case. It is worth noting that present calculations lead in fact to a ratio En /tuoH = 0.65 which favours the observation of low temperature EPR spectra displaying cubic angular pattern [4], This value is thus more reasonable than the ratio ETT/ha E= 40 previously estimated by Reynolds et al. [5]. Moreover the sb — sa separation at equilibrium is just given by 

Thus from the present calculations it is derived sh — sa = 0.14 eV for MgO Cu2+. This figure concurs with the value [21] derived from the analysis of the temperature dependence of spin-lattice relaxation, 7j. The value of the coupling coefficient for SrO Cu2+ is found to be V = 0.47 eV/A. In comparison with V = 1.05 eV/A found for MgO Cu2+ this reduction reflects the increase of R0- Therefore, the big reduction undergone by force constant, K, on going from MgO Cu2+ to SrO Cu2+ is thus the main responsible for Eji/Ua = 1.9 obtained for SrO Cu2+. This value, which is three times bigger than E]T/hojK = 0.65 derived for MgO Cu2+ can explain the observation [22] of static EPR spectra for SrO Cu2+. 

This work has been supported by the Spanish Ministerio de Ciencia y Tecnologia under project BFM2002-01730. 

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Other Jahn-Teller systems explored through DFT 455... 

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