Pressure-induced superconductivity of Ac-B-H hydrides

The search for room-temperature superconductors among high-pressure hydrides is a hot research topic. In this study, the structures, stabilities and superconducting properties of ternary Ac-B-H hydrides were studied using a genetic algorithm (GA) combined with density functional theory (DFT) calculations. It was shown that the R3̄m-AcBH₈ and I4/mmm-AcB₂H₈ structures were thermodynamically and dynamically stable above 70 and 125 GPa, respectively. In the R3̄m-AcBH₈ structure, the BH₆ unit and the dispersed H atoms were bonded to form a corrugated structure. The I4/mmm-AcB₂H₈ structure contained a cage and the Ac atom located at the cage center. The calculations of the electron-phonon coupling showed that the R3̄m-AcBH₈ and I4/mmm-AcB₂H₈ structures had T_c values of 140 K (70 GPa) and 99 K (125 GPa), respectively. The analyses of the phonon dispersion curves revealed that electron-phonon coupling was closely related to the vibrations of the B-H bonds.