Systematic Investigation of Superconducting Trends in Lanthanide-Substituted M C2H8 Ternary Hydrides

The pursuit of high-temperature superconductors represents a persistent challenge in solid-state physics. Hydrogen-rich ternary materials subjected to high pressure have emerged as particularly promising candidates. Among these, the Fm3̅m-MC2H8 family exhibits remarkable stability and compositional diversity. While LaC2H8 has been investigated, other lanthanide substituted variants remain largely unexplored. This work systematically investigates the superconducting properties of lanthanide-based MC2H8 compounds over a wide range of pressures. Calculations predicted 14 unknown superconductors within this family, with critical temperatures strongly dependent on the choice of metal M. Notably, LuC2H8 achieves the highest Tc of 99.5 K (at 200 GPa), while YbC2H8 stabilizes at the lowest pressure (30 GPa). The pressure- and temperature-dependent trends governing superconductivity in these systems have been further elucidated, providing insight into the role of lanthanide substitution in enhancing superconducting properties. These findings expand the landscape of high-temperature superconductors and highlight the potential of hydrogen-rich ternary hydrides under extreme conditions.