Pressure-Induced Hydrogen-Hydrogen Interaction in Metallic FeH Revealed by NMR

Abstract

Knowledge of the behavior of hydrogen in metal hydrides is the key for understanding their electronic properties. Here, we present an ^{1}H-NMR study of cubic FeH up to 202 GPa. We observe a distinct deviation from the ideal metallic behavior between 64 and 110 GPa that suggests pressure-induced H-H interactions. Accompanying ab initio calculations support this result, as they reveal the formation of an intercalating sublattice of electron density, which enhances the hydrogen contribution to the electronic density of states at the Fermi level. This study shows that pressure-induced H-H interactions can occur in metal hydrides at much lower compression and larger H-H distances than previously thought and stimulates an alternative pathway in the search for novel high-temperature superconductors.