High-temperature superconductivity of ternary Y–Hf–H compounds under high pressure

Abstract Compressed ternary alloy superhydrides are currently considered to be the most promising competitors for high-temperature superconducting materials. Here, the stable stoichiometries in the Y-Hf-H ternary system under pressure are comprehensively explored and four fresh phases are found: Pmna-YHfH6 and P4/mmm-YHfH7 at 200 GPa, P4/mmm-YHfH8 at 300 GPa and P-6m2-YHfH18 at 400 GPa. The four Y-Hf-H ternary phases are thermodynamically and dynamically stable at corresponding pressure. In addition, structural features, bonding characteristics, electronic properties, and superconductivity of the four ternary Y-Hf-H phases are systematically calculated and discussed. Among them, the superconducting transition temperatures (Tc) are significantly enhanced as the hydrogen content and the contribution of H atoms to the density of states at the Fermi level increase. The P-6m2-YHfH18 with high hydrogen content exhibits a high Tc value of 130 K at 400 GPa.