High-pressure and high-temperature equation of state of cobalt oxide: Implications for redox relations in Earth’s mantle

摘要: The high-pressure and high-temperature equation of state rock salt-structured cobalt oxide was measured up to 65 GPa 2600 K using synchrotron X-ray diffraction in conjunction with the laser heated diamond-anvil cell. Fitting a Mie-Gruneisen-Debye model data we find best-fit parameters V0 = 77.4 (fixed) A3, K0 190 (1) GPa, K' 3.49 (4), γ0 1.54 q 2.87 (15), θ0 517.8 (fixed). We use this newly determined existing measurements thermoelastic metal calculate Gibbs free-energy difference between phases as function pressure temperature. A comparison energetics Co/CoO system Ni/NiO predicts that below 58 CoO+Ni is stable relative NiO+Co, while above reverse true. This tipping point energy can be mapped crossing electrochemical potential two ions, suggesting becomes more siderophile than nickel increasing pressure. result qualitative agreement partition coefficients mantle core materials.