Correlations in Hot Dense Helium

Hot dense helium is studied with first-principles computer simulations. By combining path integral Monte Carlo and density functional molecular dynamics, a large temperature and density interval ranging from 1000 to 1000000 K and 0.4 to 5.4 g/cc becomes accessible to first-principles simulations and the changes in the structure of dense hot fluids can be investigated. The focus of this article are pair correlation functions between nuclei, between electrons, and between electrons and nuclei. The density and temperature dependence of these correlation functions is analyzed in order to describe the structure of the dense fluid helium at extreme conditions.Comment: accepted for publication in Journal of Physics

Ab Initio Investigation of a Possible Liquid-Liquid Phase Transition in MgSiO3 at Megabar Pressures

We perform density functional molecular dynamics simulations of liquid and solid MgSiO3 in the pressure range of 120-1600 GPa and for temperatures up to 20000 K in order to provide new insight into the nature of the liquid-liquid phase transition that was recently predicted on the basis of decaying laser shock wave experiments [Phys. Rev. Lett. 108 (2012) 065701]. However, our simulations did not show any signature of a phase transition in the liquid phase. We derive the equation of state for the liquid and solid phases and compute the shock Hugoniot curves. We discuss different thermodynamic functions and by explore alternative interpretations of the experimental findings.Comment: 15 pages, 7 figures, 2 tables, 29 reference