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Electronic spin and valence states of Fe in CaIrO 3 ‐type silicate post‐perovskite in the Earth's lowermost mantle
Author(s) -
Mao Z.,
Lin J. F.,
Jacobs C.,
Watson H. C.,
Xiao Y.,
Chow P.,
Alp E. E.,
Prakapenka V. B.
Publication year - 2010
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2010gl045021
Subject(s) - valence (chemistry) , perovskite (structure) , silicate perovskite , quadrupole splitting , mössbauer spectroscopy , spin states , silicate , materials science , synchrotron , rietveld refinement , post perovskite , crystallography , crystal structure , mantle (geology) , mineralogy , geology , condensed matter physics , chemistry , physics , geochemistry , organic chemistry , nuclear physics
The electronic spin and valence states of Fe in post‐perovskite ((Mg 0 . 75 Fe 0 . 25 )SiO 3 ) have been investigated by synchrotron X‐ray diffraction, Mössbauer and X‐ray emission spectroscopy at 142 GPa and 300 K. Rietveld refinement of the X‐ray diffraction patterns revealed that our sample was dominated by CaIrO 3 ‐type post‐perovskite. Combined Mössbauer and X‐ray emission results show that Fe in post‐perovskite is predominantly Fe 2+ (70%) in the intermediate‐spin state with extremely high quadrupole splitting of 3.77(25) mm/s. The remaining 30% Fe can be assigned to two sites. Compared with recent studies, our results indicate that the intermediate‐spin Fe 2+ is stabilized in CaIrO 3 ‐type post‐perovskite over a wide range of Fe content, whereas the low‐spin Fe 3+ is more dominant in the 2 × 1 kinked post‐perovskite structure. The characterization of these structural and compositional effects on the spin and valence states of Fe in post‐perovskite can help in understanding the geochemical and geophysical behavior of the core‐mantle region.