Emerging Electride Behavior and Metallization in Molecular Hydrogen under High Pressure

We demonstrate that the metallization of molecular hydrogen under pressure is accompanied by the emergence of an electride-like behavior, characterized by the localization of electrons in interstitial regions among H 2 molecules. This mechanism distinguishes H 2 from other molecular crystals, where metal–insulator transitions are typically driven by bond rearrangements. The presence of interstitial electrons may significantly influence the electron–phonon coupling and, consequently, the superconducting properties of molecular hydrogen. Importantly, these features persist in metal superhydrides stabilized at moderate pressures, where molecular units are retained. As a result, electride-like electronic states are an important factor in these compounds, which are among the most promising candidates for achieving high- T c superconductivity under moderate pressures.