Actinium Hydrides AcH10, AcH12, and AcH16 as High-Temperature Conventional Superconductors

The stability of numerous unexpected actinium hydrides was predicted via the evolutionary algorithm USPEX. The electron-phonon interaction was investigated for the hydrogen-richest and most symmetric phases:R(3) over bar m -AcH10, I4/mmm-AcH12, and P(6) over bar m2 -AcH16. Predicted structures of actinium hydrides are consistent with all previously studied Ac-H phases and demonstrate phonon mediated high-temperature superconductivity with T-c in the range of 204-251 K for R(3) over bar m -AcH10 at 200 GPa and 199-241 K for P(6) over bar m2 -AcH16 at 150 GPa, which was estimated by directly solving the Eliashberg equation. Actinium belongs to the series of d(1) elements (Sc-Y-La-Ac) that form high-T-c superconducting (HTSC) hydrides. Combining this observation with previous predictions of p(0)-HTSC hydrides (MgH6 and CaH6), we propose that p(0) and d(1) metals with low-lying empty orbitals tend to form phonon-mediated HTSC metal polyhydrides.