[S-IT18] Planetary cores: Structure, formation, and evolution

[SIT18-02] Compressional velocity of hcp Fe-Si alloy by inelastic X-ray scattering and composition of the inner core

*Eiji Ohtani¹, Takanori Sakairi¹, Tatsuya Sakamaki¹, Hiroshi Fukui², Seiji Kamada⁴, Satoshi Tsutsui⁵, Hiroshi Uchiyama⁵, Alfred Q Baron³ (1.Department of Earth and Planetary Materials Science, Graduate School of Science, Tohoku University, 2.Graduate School of Material Science, University of Hyogo, 3.Materials Dynamics Laboratory, RIKEN SPring-8 Center, 4.Frontier Research Institute for Interdisciplinary Sciences, Tohoku University, 5.Japan Synchrotron Radiation Research Institute)

Keywords:Fe-Si alloy, Compressional velocity, Inner core

The compressional velocity of hcp Fe0.89Si0.11 (Fe-6wt%Si) alloy was measured at pressures from 45 to 84 GPa and temperatures of 300 and 1800 K using inelsstic X-ray scattering (IXS) from laser-heated samples in diamond anvil cell (DAC). The measurement was made at beamline BL35XU of SPring8. The compressional velocity and density of the alloy are observed to follow a linear relationship at a given temperature. We found Vp=1.03Xrho-1.45+[3.8X10^(-5)X(T-300)X(rho-15.37)] including non-negligible temperature dependence for hcp-Fe0.89S90.11 alloy. The present results of compresssinal velocity and density of the alloy indicates that 3-6 wt.% od silicon in the inner core with the additional amount of nickel can explain the compressional velocity and density of the preliminary Earth reference model (PREM), assuming that the inner core temperature is 5500 K and silicon is the only light element in the inner core.