Local relaxations around Fe3+ and Cr3+ in Al sites in minerals |
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Authors: | R. Büscher K. P. Such G. Lehmann |
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Affiliation: | 1. Institut für Physikalische Chemie der Westf?lischen Wilhelms-Universit?t, Schlo?platz 4, D-4400, Münster, West Germany
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Abstract: | Second-order zero-field splitting (ZFS) parameters from the literature for Fe3+ in twelve and for Cr3+ in seven minerals substituting for Al were evaluated by application of the superposition model. For Fe3+ in monoclinic site symmetries a fair agreement of the observed splitting patterns with those calculated from the crystal structure data was observed in most cases, but the distortions for Fe3+ appear to be usually larger than those of the unrelaxed Al sites. In cases of not too large local relaxation the unknown sign of the axialZFS parameterb 0 2 could be predicted, in two cases a different sign than that reported was postulated. In cordierite and scolecite the reportedEPR spectra could thus be assigned to the sites with larger average bond distances. For Fe3+ in beryl the relaxation of the axial site can be deduced within narrow limits. For Cr3+ significantly larger differences between observed and calculatedZFS patterns are found suggesting additional relaxations due to the non-spherical electron distribution in the ground state of this ion. |
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