New structure and spin state of iron-rich (Mg,Fe)SiO[subscript 3] post-perovskite
- Stanford
There was a discrepancy between the seismic tomography and the elastic property of MgSiO{sub 3} perovskite at near the D{double_prime} zone and core boundary. Since a discovery of post-perovskite (ppv) of MgSiO{sub 3}, many investigations have made to explain the presence of low seismic velocity of the lower mantle and D{double_prime} zone. However, precise experimental structure analysis of ppv-(Mg{sub 1-x}Fe{sub x})SiO{sub 3} has never been reported because of the experimental difficulty. Fe and Mg cation distribution and ordering in ppv-(Mg,Fe)SiO{sub 3} in consideration of spins states are significant subject in lower mantle electronic and magnetic states. The present experiment aims X-ray emission study and structure analysis by Rietveld profile fitting of ppv-(Mg{sub 0.6},Fe{sub 0.4})SiO{sub 3} by the precise powder diffraction measurement. Monte Carlo calculation proposed the reliable structures of iron-rich phase of ppv-(Mg,Fe)SiO{sub 3}: Pmmn, Pmma, and Cm2m and Cmcm proposed by. The best-fit structure model with the highest reliability in the Rietveld fitting of ppv-(Mg{sub 0.6}Fe{sub 0.4})SiO{sub 3} is the structure of space group Pmma, in which Fe and Mg occupy two different sites of M1 and M2: the site occupancies are (Fe{sub 0.25}Mg{sub 0.75}) in the larger M1 site and (Fe{sub 0.55}, Mg{sub 0.45}) in the smaller M2 site. The two-site model is consistence with the previous results of X-ray emission and X-ray Moessbauer experiments.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 1002427
- Journal Information:
- J. Phys. Conf. Series, Vol. 215, Issue (1) ; 03, 2010; Conference: Tokyo, Japan
- Country of Publication:
- United States
- Language:
- ENGLISH
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