Hugoniot, sound velocity, and shock temperature of MgO to 2300 GPa

Abstract

MgO is a major constituent of the ${\text{MgO-FeO-SiO}}_{2}$ system that comprises the Earth's mantle and that of super-Earth exoplanets. Knowledge of its high-pressure behavior is important for modeling the more complex compounds. This paper presents measurements of the principal Hugoniot, sound velocity, and temperature of MgO, shocked to pressures of 710 to 2300 GPa using laser-driven compression. The Hugoniot and temperature measurements compare favorably to previous results constraining the shock response of MgO at extreme conditions. The Gr\uneisen parameter was calculated from the Hugoniot and sound velocity data and was found to be underpredicted by tabular models. The sound velocity of liquid MgO is overpredicted by models implying that the quantity of partial melt required to match decreased wave speeds in ultralow velocity zones in the lower mantle may be less than previously assumed and experiments at lower-mantle pressures are needed.