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Ab initio molecular dynamics simulations predict that CaSiO 3 perovskite melts at 5600 K at 136 GPa, and 6400 K at 300 GPa, significantly higher than MgSiO 3 perovskite. The entropy of melting (1.8 k B per atom) is much larger than that of many silicates at ambient pressure and of simple liquids and varies little with pressure. The volume of melting decreases rapidly with increasing pressure, to 3 % at 136 GPa, producing a melting slope that diminishes rapidly with pressure. We determine the melting temperature via the ZW method, combining the Z method, for which we clarify the theoretical basis, with a waiting time analysis. The ZW method results are internally confirmed by integrating the Clausius-Clapeyron equation, which also yields our results for the entropy and volume of melting. We find the eutectic composition on the MgSiO 3 -CaSiO 3 join to be x Ca  = 0.26 at 136 GPa and that metasilicate melt is denser than coexisting silicates.

Ab intio molecular dynamics simulations show that the electrical conductivity of liquid SiO 2 is semimetallic at the conditions of the deep molten mantle of early Earth and super-Earths, raising the possibility of silicate dynamos in these bodies. Whereas the electrical conductivity increases uniformly with increasing temperature, it depends nonmonotonically on compression. At very high pressure, the electrical conductivity decreases on compression, opposite to the behavior of many materials. We show that this behavior is caused by a novel compression mechanism: the development of broken charge ordering, and its influence on the electronic band gap., Competing Interests: The authors declare no conflict of interest.