Structural and Thermodynamic Properties of Magnesium-Rich Liquids at Ultrahigh Pressure

We explore the structural properties of Mg, MgO, and MgSiO3 liquids from ab initio computer simulations at conditions that are relevant for the interiors of giant planets, stars, shock compression measurements, and inertial confinement fusion experiments. Using path-integral Monte Carlo and density functional theory molecular dynamics, we derive the equation of state of magnesium-rich liquids in the regime of condensed and warm dense matter, with densities ranging from 0.32 to 86.11 g cm(-3) and temperatures from 20,000 K to 5 x 10(8) K. We study the electronic structure of magnesium as a function of density and temperature and the correlations of the atomic motion, finding an unexpected local maximum in the pair correlation functions that emerges at high densities which decreases the coordination number of elemental magnesium and reveals a higher packing. This phenomenon is not observed in other magnesium liquids, which maintain a rather constant coordination number.

Automated summary

We have investigated the structural properties of magnesium, magnesium oxide, and magnesium silicate liquids through ab initio computer simulations. By applying path-integral Monte Carlo and density functional theory molecular dynamics, we have determined the equation of state of magnesium-rich liquids under the conditions of condensed and warm dense matter. We have observed an unexpected local maximum in the pair correlation functions of high-density magnesium, which results in a decrease in the coordination number and reveals a higher packing.