P18-Geng Huayun_Photo+abstract

Stability of solid and mobile solid state of metallic hydrogen at high pressure and low temperature

Hua Y. Geng

Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, China

It has long been believed that the melting temperature of dense hydrogen will decrease continuously such that the solid metallic hydrogen becomes unstable at high pressures, and could liquefy even at the absolute zero. Using first-principles and path integral molecular dynamics simulations, we demonstrated that dense metallic hydrogen actually does not melt at zero Kelvin, even after included the nuclear quantum effect (NQE). The stability of the solid phase originates in the potential energy that prefers to ordering, with the energy gain being large enough to keep the solid structure stable against quantum fluctuations. Further increasing the pressure increases the melting temperature, unequivocally illustrates that the dip in the melting curve is a consequence of H2 dissociation, which results in a flat region from 500 GPa to 1.5 TPa. More interestingly, within this flat region, if the lattice is imperfect or coexists with the liquid phase initially, we observed that dense hydrogen will transform into a novel mobile but anisotropic state to resist liquefy, unveiling the volatility of dense hydrogen.