|
|||||
|
|
The site of Fe in Fe-bearing MgSiO3 enstatite and perovskite. a theoretical-, x-ray multiple-scattering study at Fe K-edge |
|
| Authors: | François Farges |
| Institution: | 1. Laboratoire de physique et mécanique des géomatériaux, Université Marne la Vallée, 2 alleé de la butte verte, F-93166, Noisy le Grand cedex, France 2. Laboratoire de physique des géomatériaux, URA CNRS, 734, Paris, France 3. Laboratoire pour l'utilisation du rayonnement électromagnétique LURE, Orsay, France |
| Abstract: | Two polycrystalline-, Fe-bearing MgSiO3 enstatite and perovskite have been probed by x-ray absorption near edge structure (XANES) spectroscopy at the Fe K-edge under ambient conditions. The perovskite sample was synthesized at 260 kbar and 1973 K in a multianvil apparatus. The experimental XANES spectrum has been compared to ab-initio-, x-ray multiple-scattering calculations (Feff 6 code). Calculations confirm that the Fe K-edge arises mainly from multiple scattering involving the first shell of oxygen neighbors around Fe. In Fe-enstatite, these calculations are consistent with Fe2+ as substituted in the M2 site of this orthopyroxene, in good agreement with crystal structure refinements and previous XANES studies. In perovskite, Feff 6 suggests that Fe is likely to be substituted to Mg within the (8+4)-coordinated sites of that perovskite. No evidences for 6-coordinated Fe were found. These results are consistent with a previous anharmonic analysis of the extended x-ray absorption fine structure (EXAFS) study that evidenced the presence of 8-coordinated Fe in the same perovskite sample. |
| Keywords: | |
| 本文献已被 SpringerLink 等数据库收录！ | |