Equation of State for Fe‐9.0 wt% O up to 246 GPa: Implications for Oxygen in the Earth's Outer Core

Abstract

AbstractTo constrain the amount of oxygen in Earth's outer core, the equation of sate (EoS) for Fe‐9 wt% O (Fe‐9O) was measured up to ∼246 GPa using the dynamic compression technique. The shock velocity and particle velocity relationship can be described by . Using the ideal mixing model, the isothermal equation of state for Fe‐9O at 300 K was fitted to the third‐order Birch‐Murnaghan EoS with bulk modulus GPa and its pressure derivative . Based on the EoS of Mie‐Grüneisen, the calculated adiabat coincides with our experimental data when its Grüneisen parameters are given by . Using the determined parameters, bulk sound velocities were obtained from the Hugoniot data. By comparing the pressure‐density profiles and sound velocities of Fe‐O system with the preliminary reference Earth model, it was determined that the oxygen‐rich composition does not provide a good match to the observations in the Earth's outer core.