Abstract
Abstract A simple thermodynamic model for calculating the high-pressure and high-temperature properties of MgO consistently is presented. The model explains experimental equation of state (EOS) to ∼220 GPa at room temperature and shock-wave EOS to ∼200 GPa very well. The calculated Hugoniot temperature amounts to 3400 K at 200 GPa. The input parameters are the volume of the unit cell, V0, bulk modulus, K0, its pressure derivative, K0′, Debye temperature, Θ0, and a parameter relating to the shear modulus, f44, all in the static lattice at zero pressure which are estimated from experimental data at room temperature and zero pressure. The calculated thermal expansivity, α, and Anderson–Gruneisen parameters, δT and δS, at zero pressure are in agreement with experimental data to 1000–1250 K and those to 1800 K, respectively. Our model explains also experimental velocities vp and vs of compressional and shear waves to 1800 K at zero pressure very well. The pressure-dependence of α, vp and vs at room temperature agree reasonably with experimental data to 36 GPa at room temperature. Applying our model to magnesiowustite, we have calculated the thermal EOS and shock-wave EOS in agreement with experimental data. The implication of our result together with our previous one of magnesium-silicate perovskite for the composition of the lower mantle is briefly discussed.
Published Version
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