ELNES SPECTROSCOPY OF MIXED SI COORDINATION MINERALS

Si K-and L-edge ELNES spectroscopy and multiple-scattering (MS) calcul ations are used to examine mixed Si coordination compounds varying in Si-VI:Si-IV ratio. As in previous studies, the edges are influenced ma inly by silicon coordination (tetrahedral vs. octahedral), as supporte d by the MS calculations. We demonstrate two methods semi-quantitative ly to extract the value of Si-VI/ (Si-VI+Si-IV): (1) A linear relation ship between the L-2,L-3-L-1 splitting and Si-VI/(Si-VI+Si-IV) is obse rved, (2) a fitting method based on the coaddition of reference tetrah edral and octahedral Si spectra is applied to both Si K- and L-edge EL NES spectra.