The site of Fe in Fe-bearing MgSiO3enstatite and perovskite. a theoretical-, x-ray multiple-scattering study at Fe K-edge

✍ Scribed by François Farges

• Publisher: Springer-Verlag
• Year: 1995
• Tongue: English
• Weight: 533 KB
• Volume: 22
• Category: Article
• ISSN: 0342-1791
• DOI: 10.1007/bf00202772

✦ Synopsis

Two polycrystalline-, Fe-bearing MgSiO s 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 n~ultianvil 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 Fe 2+ 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.