XAFS characterization of the structural site of Yb in synthetic pyrope andgrossular garnets. II: XANES full multiple scattering calculations at the Yb L-I- and L-III-edges

We present an X-ray absorption near-edge structure study performed at the Y b L-I- and L-III-edges on synthetic pyrope (Mg3Al2Si3O12) and grossular (Ca 3Al2Si3O12) garnets containing about 1% wt of Yb, For the first time Yb L-e dge XANES spectra are analyzed by full multiple scattering theory using clu sters of different sizes and different final-state potentials. A comparison between experimental spectra and model calculations indicates that Yb3+ en ters the dodecahedral X-site in both pyrope and grossular, in agreement wit h the results of an EXAFS study. Based on the present results, the charge b alancing substitution mechanism required by the replacement of divalent Mg and Ca cations with trivalent Yb3+ is discussed in terms of vacancies in do decahedral sites surrounding the central Yb3+ absorber.