Theory of high-pressure phases of hydrogen

Abstract

The electronic structure and enthalpy are calculated as a function of pressure for several phases of molecular and metallic hydrogen. For the molecular solid we offer an alternative interpretation of the recently observed transition at 1.5 Mbar. For the intermediate-pressure range from 3.8\ifmmode\pm\else\textpm\fi{}0.5 to 8.6\ifmmode\pm\else\textpm\fi{}1 Mbar, the most stable structures have low coordination numbers and are anisotropic. Among them a metallic filamentary primitive hexagonal phase is particularly stable. For higher pressures, the bcc structure is the most stable.