Coordination chemistry of Ti(IV) in silicate glasses and melts: I. XAFS study of titanium coordination in oxide model compounds
- Universite de Marne-la-vallee, Grand (France)
- Stanford Univ., CA (United States)
- Univ. of Washington, Seattle, WA (United States)
The coordination environment of Ti(IV) in a variety of Ti-bearing crystalline oxide and silicate model compounds has been studied using Ti K-edge x-ray absorption fine structure (XAFS) spectroscopy at ambient temperature and pressure in order to provide a quantitative basis for interpreting Ti K-edge XAFS spectra of silicate glasses and melts. Pre-edge features of Ti K-edge XAFS spectra can be used to derive accurate information on the local coordination environment of Ti only if both pre-edge position and heights are considered. Using these features, it is also possible to distinguish between one coordination environment vs. a mixture of several others (e.g., {sup [4]}Ti vs. {sup [5]}Ti + {sup [6]}Ti). Quantitative analysis of the Ti x-ray absorption near edge structure (XANES) spectra, based on ab-initio multiple-scattering calculations for a variety of Ti-containing clusters and anharmonic analysis of the normalized XAFS oscillations, show that O first neighbors and alkali/alkaline-earth second neighbors around Ti contribute to the XAFS spectra. However, second neighbors are more prominent in the XANES region because the effects of disorder associated with these contributions are less important in this region than in the extended XAFS (EXAFS) region. Therefore, XANES spectra can be used to probe the degree of disorder in the medium-range structural environment around Ti in crystalline and amorphous materials, including Ti-bearing a periodic structures, such as metamict, glassy, and molten compounds. 125 refs., 10 figs., 2 tabs.
- OSTI ID:
- 476824
- Journal Information:
- Geochimica et Cosmochimica Acta, Vol. 60, Issue 16; Other Information: PBD: Aug 1996
- Country of Publication:
- United States
- Language:
- English
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