Understanding high pressure molecular hydrogen with a hierarchical machine-learned potential.

ABSTRACT: The hydrogen phase diagram has several unusual features which are well reproduced by density functional calculations. Unfortunately, these calculations do not provide good physical insights into why those features occur. Here, we present a fast interatomic potential, which reproduces the molecular hydrogen phases: orientationally disordered Phase I; broken-symmetry Phase II and reentrant melt curve. The H₂ vibrational frequency drops at high pressure because of increased coupling between neighbouring molecules, not bond weakening. Liquid H₂ is denser than coexisting close-packed solid at high pressure because the favored molecular orientation switches from quadrupole-energy-minimizing to steric-repulsion-minimizing. The latter allows molecules to get closer together,

SUBMITTER: Zong H 

PROVIDER: S-EPMC7538439 | biostudies-literature | 2020 Oct

REPOSITORIES: biostudies-literature