Title

Investigation of the structural environment of Ta in a silicate glass and water system under high P-T conditions

Abstract

In situ Ta L3-edge XAS measurements have been made from a Ta (~ 1400 ppm)-bearing peraluminous silicate glass + H2O system to 960 °C and ~ 0.6 GPa. A white-line doublet separated by ~ 4 eV occurs in the Ta L3-edge XANES and results from octahedral crystal field splitting of the Ta 5d levels due to the local structure surrounding Ta coordinated by Qn-species (n = number of bridging oxygen atoms shared between SiO4 and AlO4 units) in the silicate glass/melt + H2O system. The XANES spectra measured from the hydrous silicate glass/melt and from the silicate-rich aqueous fluid have been analyzed using multi-peak fitting techniques. The white-line doublet intensity varies with increasing P-T conditions of the silicate glass/melt + water system, indicating a shift in the electronic density of states in the vicinity of quasi bound Ta 5d states probed by the 2p3/2 core photoelectron. Ab initio modeling of the XANES indicates that water dissolution causes distortion of local structure surrounding the 6-fold coordinated Ta-Qn clusters in the hydrous silicate glass/melt and in the silicate-rich aqueous fluid. Calculation of the angular-momentum projected density of states (l-DOS) shows that the upper doublet level quasi-bound d-DOS is steadily reduced with increasing distortion of the local structure surrounding Ta-Qn clusters.

Department(s)

Physics, Astronomy, and Materials Science

Document Type

Article

DOI

https://doi.org/10.1016/j.jnoncrysol.2013.03.011

Keywords

X-ray absorption, high pressure, silicate glass-melt structure, high field strength elements, water dissolution in silicate melt

Publication Date

2013

Recommended Citation

Mayanovic, Robert A., Hao Yan, Alan J. Anderson, and Giulio Solferino. "Investigation of the structural environment of Ta in a silicate glass and water system under high P–T conditions." Journal of non-crystalline solids 368 (2013): 71-78.

Journal Title

Journal of non-crystalline solids

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