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

The recent discovery of room-temperature superconductivity in LaSc₂H₂₄ 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 $Fm\overline{3}m$ La₂ScH₃₆ aligns with that of observed secondary phase. First-principles calculations reveal that stoichiometric La₂ScH₃₆ 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 La₂ScH_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.