Promising Room-Temperature Superconductor in the La–Sc–H System at High Pressure

The recent discovery of room-temperature superconductivity in LaSc 2 H 24 has contributed to high-pressure research. Experimental measurements suggest the presence of an undetermined secondary phase in certain samples. Leveraging machine-learning-accelerated crystal structure prediction, we performed an extensive search for the La–Sc–H system at 250 GPa, idenifying a series of metastable ternary hydrides. We found that the structure of F m 3 ¯ m La 2 ScH 36 aligns with that of observed secondary phase. First-principles calculations reveal that stoichiometric La 2 ScH 36 is a potential room-temperature superconductor with a T c of 369–412 K. Accounting for structural stability, we propose that the secondary phase adopts a hydrogen-deficient La 2 ScH 36– x (0 < x < 2) configuration, yielding a predicted T c of 261–282 K, consistent with experimental measurements. Our findings provide a promising structural assignment for the observed secondary phase and position the La–Sc–H system as a platform for hosting diverse room-temperature superconducting configurations.