First-order liquid-liquid phase transition in dense hydrogen

Abstract

We use ab initio molecular-dynamics simulations to study the nonmetal-to-metal transition in dense liquid hydrogen. By calculating the equation of state of hydrogen at high pressures up to several megabars and temperatures above the melting line up to 1500 K we confirm the first-order nature of this transition at these temperatures. We characterize both phases based on equation of state data, the electrical conductivity, and the pair-correlation functions, which are all derived self-consistently from these simulations. We locate the respective transition line in the phase diagram and give an estimate for its critical point. We compare with available experimental data and other theoretical predictions.