The six lower electronic transitions observed in octahedral fluoride compounds containing Cr3+are calculated in the framework of an openhyphen;shell SCF MO methodology. An initial, isolatedhyphen;cluster description is presented and compared with a more elaborate representation which includes the external lattice potential, a cluster correlation energy correction, and spinhyphen;orbit and configuration interactions. When these refinements are included, the six transition energies observed in K2NaCrF6are computed with a mean deviation of 0.6 kK, a sixth of the initial value. The theoretical equilibrium distance is only 0.014 Aring; removed from experiment. CI and cluster correlation energies play a competitive role in locating thet3doublets; the calculation placest3minus;2T1gabovet3minus;2Egand belowt2eminus;4T2g. Due to the variation of spinhyphen;orbit interaction with distance, these levels change in character so rapidly that a more realistic procedure than the usual Franckndash;Condon approximation has been employed in the calculation of the transition intensity pattern via the magnetic dipole mechanism. Surprisingly, the equilibrium distance of 1Ggr;7minus;4T2gis computed only 0.01 Aring; greater than that of the ground state, but this small separation still allows at least one vibrational overtone to have observable intensity. Some of our results may be related to cubic oxide compounds and in this context quantitative discussions are presented about the doublethyphen;quartet mixing, the structure of the4A2grarr;2T2gbroad band, and the Stokes shift observed in the emission spectra of those crystals.
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