First-principles modelling of hydrogen-rich planetary materials*

Accurate models of the interior structure of planetary bodies, in our or other solar systems, are key to understanding their formation, their evolution to the present day, and many of their properties. The stratification (or lack thereof) of molecular mixtures inside icy planets’ mantles influences their luminosity and cooling rates; and the presence (or not) of water stored inside rocky planets’ mantles influences their convection rates, the magnitude of plate tectonics and presence of surface water. In my talk I will give an overview of our ongoing research aimed at a better understanding of planetary materials using electronic structure calculations, focussing on hydrogen-containing systems on several different pressure scales. For molecular gas hydrates stabilized in the kbar range, crucial in the formation of icy moons and planets, I will show how wave-function based calculations can overcome density functionals’ ambiguities in capturing weak host-guest interactions [1]. For hydrous minerals, which store water inside Earth’s mantle in the GPa range, I will illustrate how crystal structure prediction methodology can help develop a more complete picture on their formation and internal phase transformations [2]. Lastly, I will discuss the properties of mixtures of planetary ices at conditions found in the mantle of Neptune-like bodies, at pressures beyond 1 Mbar and high temperatures [3,4].

[1] J. Kosata, P. Merkl, P. Teeratchanan, and A. Hermann, J. Phys. Chem. Lett. 9, 5624 (2018)
[2] A. Hermann, and M. Mookherjee, Proc. Natl. Acad. Sci. 113, 13971 (2016)
[3] V. Naden Robinson, Y. Wang, Y. Ma, and A. Hermann, Proc. Natl. Acad. Sci. 114, 9003(2017)
[4] V. Naden Robinson, M. Marques, Y. Wang, Y. Ma, and A. Hermann, in review.