Superconductivity and superionicity in doped rare-earth metal hydrides: Insights from first-principle calculations

Hydrides have attracted elemental attention due to their potential for high-temperature superconductivity under pressure, with recent discoveries pushing the boundaries of this field. In this study, we systematically investigated the superconducting and superionic properties of rare-earth metal hydrides with Fm 3 ̅ m symmetry, doped with carbon and nitrogen. By introducing highly electronegative elements at the tetrahedral sites or octahedral sites, we explored the effects of doping and hydrogen vacancies. Using first-principles calculations, we identified several metastable structures at ambient pressure with superconducting transition temperatures ( T c ) reaching up to 14 K. Additionally, ab initio molecular dynamics simulations revealed superionic behavior, which coexists with superconductivity in these compounds. The electride nature of pure rare-earth metals plays a crucial role in driving superconductivity at low temperatures and enabling the transition to superionicity at higher temperatures. Our results highlight the potential of rare-earth metal hydrides as a novel class of superconductors, exhibiting both superconductivity and superionicity, with intriguing implications for future materials design.