Sound velocity measurements in dhcp-FeH up to 70 GPa with inelastic X-ray scattering: Implications for the composition of the Earth's core |
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| Authors: | Yuki Shibazaki Eiji Ohtani Hiroshi Fukui Takeshi Sakai Seiji Kamada Daisuke Ishikawa Satoshi Tsutsui Alfred QR Baron Naoya Nishitani Naohisa Hirao Kenichi Takemura |
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| Institution: | 1. Department of Earth and Planetary Material Sciences, Tohoku University, 6-3 Aoba, Aramaki, Aoba-ku, Sendai 980-8578, Japan;2. Materials Dynamics Laboratory, RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo 679-5148, Japan;3. Graduate School of Material Science, University of Hyogo, 3-2-1, Kamigohri, Hyogo 678-1279, Japan;4. Japan Synchrotron Radiation Research Institute (SPring-8/JASRI), 1-1-1 Kouto, Sayo 679-5198, Japan;5. Materials Processing Unit, National Institute for Materials Science (NIMS), Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan |
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| Abstract: | We have determined the density evolution of the sound velocity of dhcp-FeHx (x ≈ 1) up to 70 GPa at room temperature, by inelastic X-ray scattering and by X-ray diffraction. We find that the variation of VP with density is different for the ferromagnetic and nonmagnetic dhcp-FeHx, and that only nonmagnetic dhcp-FeHx follows Birch's law. Combining our results with Birch's law for iron and assuming an ideal two-component mixing model, we obtain an upper bound of the hydrogen content in the Earth's inner core, 0.23(6) wt.% H, corresponding to FeH0.13(3). The iron alloy with 0.23(6) wt.% H can satisfy the density, and compressional and shear sound velocities of the PREM inner core, assuming that there are no other light elements in the inner core. |
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