Spin state of ferric iron in MgSiO3 perovskite and its effect on elastic properties |
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| Authors: | Krystle Catalli Sang-Heon Shim Vitali B Prakapenka Jiyong Zhao Wolfgang Sturhahn Paul Chow Yuming Xiao Haozhe Liu Hyunchae Cynn William J Evans |
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| Institution: | 1. Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA;2. GeoSoilEnviroCARS, University of Chicago, Argonne National Laboratory, Argonne, IL 60439, USA;3. Sector 3, Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA;4. HPCAT, Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA;5. Lawrence Livermore National Laboratory, 7000 East Ave, Livermore, CA 94550, USA;1. Department of Physics, National Institute of Technology Kurukshetra, Haryana 136119, India;2. School of Materials Science and Technology, Indian Institute of Technology (BHU), Varanasi 221005, India;1. Institute for Research on Combustion-CNR, P.le Tecchio 80, 80125 Naples, Italy;2. DICMAPI, University of Naples Federico II, P.le Tecchio 80, 80125 Naples, Italy;1. Geodynamics Research Center, Ehime University, Ehime 790-8577, Japan;2. Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo 152-8550, Japan;3. Japan Synchrotron Radiation Research Institute, Hyogo 679-5198, Japan;1. Department of Chemical Engineering, University of Naples Federico II, P.le Tecchio 80, 80125 Naples, Italy;2. Institute of Researches on Combustion, CNR, P.le Tecchio 80, 80125 Naples, Italy;1. Nanosystem Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan;2. Department of Applied Molecular Chemistry, College of Industrial Technology, Nihon University, Izumi-cho 1-2-1, Narashino, Chiba 275-8575, Japan;3. Electronics and Photonics Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan;4. Materials Design and Characterization Laboratory, Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan;5. Department of Material and Environmental Chemistry, Utsunomiya University, 7-1-2 Yoto, Utsunomiya 321-8585, Japan;1. Department of Geosciences, Princeton University, Princeton, NJ 08544, USA;2. High-Pressure Collaborative Access Team, Carnegie Institution of Washington, 9700 South Cass Avenue, Argonne, IL 60439, USA;3. Center for Advanced Radiation Sources, The University of Chicago, 9700 South Cass Avenue, Argonne, IL 60439, USA |
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| Abstract: | Recent studies have indicated that a significant amount of iron in MgSiO3 perovskite (Pv) is Fe3+ (Fe3+/ΣFe = 10–60%) due to crystal chemistry effects at high pressure (P) and that Fe3+ is more likely than Fe2+ to undergo a high-spin (HS) to low-spin (LS) transition in Pv in the mantle. We have measured synchrotron Mössbauer spectroscopy (SMS), X-ray emission spectroscopy (XES), and X-ray diffraction (XRD) of Pv with all iron in Fe3+ in the laser-heated diamond-anvil cell to over 100 GPa. Fe3+ increases the anisotropy of the Pv unit cell, whereas Fe2+ decreases it. In Pv synthesized above 50 GPa, Fe3+ enters into both the dodecahedral (A) and octahedral (B) sites approximately equally, suggesting charge coupled substitution. Combining SMS and XES, we found that the LS population in the B site gradually increases with pressure up to 50–60 GPa where all Fe3+ in the B site becomes LS, while Fe3+ in the A site remains HS to at least 136 GPa. Fe3+ makes Pv more compressible than Mg-endmember below 50 GPa because of the gradual spin transition in the B site together with lattice compression. The completion of the spin transition at 50–60 GPa increases bulk modulus with no associated change in density. This elasticity change can be a useful seismic probe for investigating compositional heterogeneities associated with Fe3+. |
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