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

Journal Article · Wed May 01 00:00:00 EDT 2013 · Journal of Non-Crystalline Solids

DOI:https://doi.org/10.1016/j.jnoncrysol.2013.03.011· OSTI ID:1083329

Mayanovic, Robert A.; Yan, Hao; Anderson, Alan J.; Solferino, Giulio

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 2p_3/2 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.

• Research Organization: Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
• Sponsoring Organization: FOREIGNDOE - BASIC ENERGY SCIENCES
• OSTI ID: 1083329
• Journal Information: Journal of Non-Crystalline Solids, Vol. 368; ISSN 0022-3093
• Publisher: Elsevier
• Country of Publication: United States
• Language: ENGLISH