Superconductivity and stability study of ASc₂H₂₄ (A = Y, La, Ac) under high pressure

Inspired by the high-temperature superconductivity of LaSc₂H₂₄ at room temperature, we substitute La with the A-site element and investigate the superconducting and stability properties of the ternary hydrides ASc₂H₂₄ (A = Y, La, Ac) under high-pressure conditions. First-principles calculations reveal that the predicted structure AcSc₂H₂₄ not only remains dynamically stable under ultrahigh pressures (400-500 GPa) but also exhibits notable superconducting transition temperatures (T_c) around 207.6 K at 400 GPa. Interestingly, as the atomic mass of the A-site element increases, the T_c of the structure gradually decreases, while the density of states (DOS) at the Fermi level also decreases. This trend underscores the critical role of hydrogen-derived DOS at the Fermi level in determining the superconducting performance of these hydrides. In particular, we show that the bonding properties of AcSc₂H₂₄ change significantly at 500 GPa, and thus highlight the significance of atom substitution as well as pressure-induced bonding evolution in respect of superconducting material design.