Prediction of potential high-temperature superconductivity in ternary Y-Hf-H compounds under high pressure

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 in theory and four fresh phases are predicted: 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. As the hydrogen content and the density of states of H atoms at the Fermi level increase, the superconducting transition temperatures (T_c) of Y-Hf-H system are significantly enhanced. The P-6m2-YHfH₁₈ with high hydrogen content exhibits a high calculated T_c value of 130 K at 400 GPa.