Isothermal compression behavior of (Mg,Fe)O using neon as a pressure medium |
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| Authors: | Kirill K Zhuravlev J M Jackson A S Wolf J K Wicks J Yan S M Clark |
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| Institution: | (1) Seismological Laboratory, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, 91125, USA;(2) Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA;(3) Present address: Department of Chemistry, University of Western Ontario, London, ON, N6A 5B7, Canada |
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| Abstract: | We present isothermal volume compression behavior of two polycrystalline (Mg,Fe)O samples with FeO = 39 and 78 mol% up to
~90 GPa at 300 K using synchrotron X-ray diffraction and neon as a pressure-transmitting medium. For the iron-rich (Mg0.22Fe0.78)O sample, a structural transition from the B1 structure to a rhombohedral structure was observed at 41.6 GPa, with no further
indication of changes in structural or compression behavior changes up to 93 GPa. In contrast, a change in the compression
behavior of (Mg0.61Fe0.39)O was observed during compression at P ≥ 71 GPa and is indicative of a spin crossover occurring in the Fe2+ component of (Mg0.61Fe0.39)O. The low-spin state exhibited a volume collapse of ~3.5%, which is a larger value than what was observed for a similar
composition in a laser-heated NaCl medium. Upon decompression, the volume of the high-spin state was recovered at approximately
65 GPa. We therefore bracket the spin crossover at 65 ≤ P (GPa) ≤ 77 at 300 K (Mg0.61Fe0.39)O. We observed no deviation from the B1 structure in (Mg0.61Fe0.39)O throughout the pressure range investigated. |
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