Dissociation of Fluid Hydrogen at High Pressure and Temperature

Studying the dissociation of liquid hydrogen at extreme high pressure and temperature is very helpful for understanding its equation of state and thermodynamic properties. Based the previous ab-initio simulation results which were in good agreement with various experiments, the values of dissociation degree of hot dense hydrogen at different state points were calculated via the coordination number, and then the effects of dissociation in shocked deuterium on its thermodynamic properties were discussed. The results show that the deuterium is mostly a diatomic fluid blow 20GPa, and almost a monatomic fluid above 53GPa, with a dissociation of 11.5% and 90% respectively, and thus a fluid composed of D2 and D between 20GPa and 53GPa. Furthermore, two critical lines of liquid hydrogen in the T-ρ and T-P space when its dissociation nearly occurs or ends were mapped, and a suggestion that there is at least 50% dissociation at the onset of metallization in the dense liquid hydrogen was made.