Physical properties of MgO at deep planetary conditions

Using ab initio molecular dynamics simulations, we calculate the physical properties of MgO at conditions extending from the ones encountered in the Earth mantle up to the ones anticipated in giant planet interiors such as Jupiter. We pay particular attention to the high-pressure melting temperature throughout this large density range as this is a key ingredient for building accurate planetary interior models with a realistic description of their inner cores. We compare our simulation results with previous ab initio calculations that have been so far limited to the pressure range corresponding to the Earth mantle and the B1-B2 transition around 6 Mbar. We provide our results for both the equation of state and high-pressure melting curve in parametric forms for direct use in planetary models. Finally, we compare our predictions of the high-pressure melting temperature with various planetary interior profiles to deduce the state of differentiated layer within the core made of MgO in differentiated cores of various types of planets and exoplanets.

Figure 1

(a) EOS points obtained with simulations initially started in the B1 phase. (b) EOS points obtained with simulations initially started in the B2 phase.

Figure 2

(a) High-pressure melting temperature obtained with simulations initially started using the B1 and B2 phases. (b) Zoom at pressures below 10 Mbar. The color scheme indicates the final state after equilibration in the liquid (red) and in the solid (blue).

Figure 3

(a) Comparison between the high-pressure melting curve obtained in this work and previous results. (b) Comparison between the slopes of the melting curve $(dT/dP)$ obtained in this study with previous work.

Figure 4

Comparison between the B2 high-pressure melting temperature with planetary interior profiles.