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 Tc up to ∼50 K at 50 GPa. This study provides useful guidance for expanding the search directions for conventional superconductors under lower-pressure conditions.