Simulation of ab Initio Dynamics of the Formation of Metastable Conducting Solid Hydrogen

Abstract

Density-functional theory (DFT) is applied to the calculation of the equation of state, the pair correlation function (PCF), and the static electrical conductivity of solid hydrogen near the transition point to the conducting state. It is found that the pressure versus density exhibits hysteresis at temperature of 100 K under compression followed by expansion. The overlapping of the isotherm branches of molecular and nonmolecular phases of solid hydrogen is observed, which corresponds to the domain of existence of metastable states. The value of this region is 275 GPa. Under compression, a transition of solid molecular hydrogen from monoclinic structure with C2/c symmetry to a conducting nonmolecular state with orthorhombic C2221 structure through an intermediate conducting molecular phase with orthorhombic Cmca-4 structure is observed. Under expansion, a transition of the conducting nonmolecular state with C2221 symmetry of the unit cell to a conducting molecular phase with Cmca-4 symmetry occurs through an intermediate nonmolecular phase with P21/c symmetry. It is shown that the conducting nonmolecular crystalline hydrogen with P21/c symmetry persists down to a pressure of 350 GPa.