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XAFS characterization of the structural site of Yb in synthetic pyrope and grossular garnets. II: XANES full multiple scattering calculations at the Yb LI- and LIII-edges |
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| Authors: | S Quartieri J Chaboy G Antonioli C A Geiger |
| Institution: | Istituto di Scienze della Terra, Salita Sperone 31, 98166 Messina S. Agata, Italy e-mail: simonaq@unimo.it Tel.: +39-090-6765103; Fax: +39-090-392333, IT Instituto de Ciencia de Materiales de Aragón and Departamento de Física de la Materia Condensada, Plaza S. Francisco s/n. 50009 Zaragoza, Spain, ES INFM and Dipartimento di Fisica, Viale delle Scienze, 43100 Parma, Italy, IT Institut Für Geowissenschaften, Olshausenstr 40, 24098 Kiel, Germany, DE |
| Abstract: | We present an X-ray absorption near-edge structure study performed at the Yb LI- and LIII-edges on synthetic pyrope (Mg3Al2Si3O12) and grossular (Ca3Al2Si3O12) garnets containing about 1% wt of Yb. For the first time Yb L-edge XANES spectra are analyzed by full multiple scattering theory using clusters of different sizes and different final-state potentials. A comparison between experimental spectra and model calculations indicates that Yb3+ enters the dodecahedral X-site in both pyrope and grossular, in agreement with the results of an EXAFS study. Based on the present results, the charge balancing substitution mechanism required by the replacement of divalent Mg and Ca cations with trivalent Yb3+ is discussed in terms of vacancies in dodecahedral sites surrounding the central Yb3+ absorber. Received: 7 December 1998 / Revised, accepted: 7 May 1999 |
| Keywords: | XANES Full multiple scattering calculation Garnet Ytterbium |
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