Magnesium oxide at extreme temperatures and pressures studied with first-principles simulations

What is it about?

Magnesium oxide (MgO) is a very abundant mineral in the universe that is believed to be a key components of rocky exoplanets. Its properties at the extreme conditions of planetary interiors still remain unknown, and they are necessary to understand how these planets form and evolve. Here, we present results from computer simulations of MgO based on quantum mechanics in the regime of warm dense matter, with densities ranging from 0.35 to 71 g/cc and temperatures from 10 000 K to 5 × 100 000 000 K. These conditions are relevant for the interiors of giant planets and stars as well as for shock wave compression measurements and inertial confinement fusion experiments. We study the electronic structure of MgO and the ionization mechanisms as a function of density and temperature. We show that the L-shell orbitals of magnesium and oxygen hybridize at high density. This results into a gradual ionization of the L-shell with increasing density and temperature. In this regard, MgO behaves differently from pure oxygen, which is reflected in the shape of the MgO principal shock Hugoniot curve. The curve of oxygen shows two compression maxima, while that of MgO shows only one. We predict a maximum compression ratio of 4.66 to occur for a temperature of 6.73 ×107 K. Finally we study how multiple shocks and ramp waves can be used to cover a large range of densities and temperatures.

Featured Image

Photo by Waldemar Brandt on Unsplash

Photo by Waldemar Brandt on Unsplash

Why is it important?

Being one of the most abundant minerals in the universe and one of the most likely components of the mantle of rocky exoplanets, MgO is important for planetary science and geophysics, as understanding its properties means to understand how planets form and evolve.