Pressure-induced superconductivity in ternary yttrium borohydride systems

Driven by the excitement surrounding high-temperature superconductivity in hydrides, we systematically investigated the structures, electronic properties, and superconductivity of ternary Y-B-H compounds using first-principles calculations combined with a genetic algorithm for structure search. Five stable phases (YBH, YBH₂, YBH₁₀, YB₂H₆ and YB₂H₁₀) were predicted at specified pressures. Several structural building units, such as boron rings, folded boron chains, BH₄ tetrahedrons, and dumbbell-shaped B₂H₆, were observed in these stable phases. The metallic phase C2-YB₂H₆ with dumbbell-shaped B₂H₆ units was found to be dynamically stable at 50 GPa and thermodynamically stable at 100 GPa. Compared to the binary B-H superconducting system, the addition of the rare-earth element Y significantly reduces the stabilization pressure for the ternary phases. Electron-phonon coupling calculations showed that C2-YB₂H₆ and the metastable YBH₅ (P3m1 and F4̄3m) and YB₂H₁₂ (P₁) phases with tetrahedral BH₄ units are superconductors at a pressure of 50 GPa. Among them, F4̄3m-YBH₅ exhibits strong electron-phonon coupling, which drives the superconducting T_c up to ∼50 K at 50 GPa. This study provides useful guidance for expanding the search directions for conventional superconductors under lower-pressure conditions.