First-principles equation of state of liquid hydrogen and dissociative transition

The properties of dense hot hydrogen, in particular the phase transition between the molecular insulating and atomic conductive states, are important in the fields of astrophysics and high-pressure physics. Previousab initiocalculations suggested the metallization in liquid hydrogen, accompanied by dissociation, is a first-order phase transition and ends at a critical point in temperature range between 1500 and 2000 K and pressure close to 100 GPa. Using density functional theoretical molecular dynamics simulations, we report a first-principles equation of state of hydrogen that covers dissociation transition conditions at densities ranging from 0.20 to 1.00 g/cc and temperatures of 600-9000 K. Our results clearly indicate that a drop in pressure and a sharp structural change still occur as the system transforms from a diatomic to monoatomic phase at temperatures above 2000 K, and support the first-order phase transition in liquid hydrogen would end in the temperature about 4500 K.

Automated summary

The properties and phase transition of dense hot hydrogen, particularly in the transition from molecular insulating to atomic conductive states, are of significance in astrophysics and high-pressure physics. The metallization and dissociation in liquid hydrogen have been suggested to be a first-order phase transition, with a critical point in the temperature range of 1500-2000 K and pressure close to 100 GPa. Results from density functional theoretical molecular dynamics simulations indicate a drop in pressure and structural change as hydrogen transitions from diatomic to monoatomic phase above 2000 K, supporting a first-order phase transition in liquid hydrogen ending at around 4500 K.