Superconducting and superionic behaviors of electride Na₆C under moderate pressure

Electrides exhibiting diverse electride states, superconductivity, and superionic behavior have attracted considerable attention for elucidating intricate chemical bonding and particle interactions. However, due to the scarcity of electrides exhibiting three-dimensional electride states, the associated properties abovementioned remain elusive. Here, we propose an electride C2/m-Na₆C that exhibits peculiar three-dimensional electride states under 30 GPa and maintains dynamic stability at ambient conditions. Our electron-phonon interaction calculations reveal that the T _c of 0.051 K at 30 GPa arises from the scattering Na/C sp-hybridized electrons by Na/C-derived low-frequency phonons, rather than three-dimensional electride states. Further molecular dynamics simulations indicate that this structure exhibits superionic states at 1,200 K, where the unusually heavy sodium atoms exhibit diffusive behavior. This anomalous behavior can be attributed to the duality of formation process of three-dimensional electride states and their multi-center bonding effect. Our study provides theoretical guidance for further investigation into the diverse physical characteristics of electrides.