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Experimental Ti K-edge x-ray-absorption near-edge structure (XANES) spectra for a variety of Ti (IV) -bearing crystalline oxide model compounds are compared with those calculated using the ab initio multiple-scattering code FEFF7. A scattering-theoretic interpretation of various features in the experimental spectra, including pre-edge and main-edge peaks, is presented together with an interpretation of the effects of disorder. The observed pre-edge features are found to vary in both position (by 20. 1eV) and normalized height (from 0. 04 to 1. 00. 05) as a function of Ti coordination (4, 5, or 6 oxygen nearest neighbors), in agreement with calculations. In aperiodic oxide compounds where the Ti coordination is unknown (e. g. , titanosilicate glasses and melts), pre-edge position and height can be used to derive reliable information on Ti coordination chemistry. For example, one can distinguish between fivefold coordinated Ti (i. e. , TiO₅) and a 50: 50 mixture of fourfold- and sixfold-coordinated Ti (i. e. , TiO₄ vs TiO₆). Finally, it is proposed that the intensity of the main-edge features can be used as a probe of disorder in the short- and medium-range environment of Ti. This is exemplified by Ti XANES studies of the effect of radiation damage on CaTiSiO₅ and the melting of K₂TiSi₂O₇ glass at high temperature.
Farges et al. (Tue,) studied this question.