Ab initio simulation of heat and charge transport in water at planetary pT conditions

The transport properties of water at extreme pT conditions govern the evolution of icy planets, such as Uranus and Neptune, and moons, such as Europa or Encelado. New theoretical and data-analysis methods have been recently developed to estimate accurate transport coefficients of electronically gapped materials from ab initio equilibrium molecular dynamics and the Green-Kubo theory of linear response [1-3]. In this talk we report on recent results of the application of these methods to heat and charge transport in water at the extreme pT conditions occurring in the interior of icy giants, in all the different relevant phases (partially dissociated liquid, solid, and super-ionic) [4]. These results are finally employed to build a model of the thermal evolution of Uranus, which accounts for its hitherto poorly understood very low luminosity.

[1] A. Marcolongo, P.Umari, and S. Baroni, Nature Physics 12, 80–84 (2016)
[2] F. Grasselli and S. Baroni, Nature Physics 15, 967–972 (2019)
[3] R. Bertossa, F. Grasselli, L. Ercole, and S. Baroni, Phys. Rev. Lett. 122, 255901 (2019)
[4] F. Grasselli, L. Stixrude, S. Baroni, in preparation