Superconductivity and magnetism in compressed actinium-beryllium-hydrogen alloys

The discovery of new high-temperature superconductors is one of the most critical problems in materials, chemistry, and physics. This work systematically investigates fluorite-like structures of XBeH8 (X is Ac, Th, Pa, U, and Np) to gain physical insight into the pressure effects on the properties. Our results reveal that AcBeH8 and ThBeH8 are two potential high-temperature superconductors, where AcBeH8 reaching a superconducting transition temperature of 284.11 K at 150 GPa and even a value of 203.29 K at 50 GPa, ThBeH8 has Tc is 217.65 K at 200 GPa, and the predicted results provide strong candidates for achieving high temperature or even room temperature superconductivity. The analysis of pressure effects demonstrates unusual charge transfer and atomic structure in the system, with s-f migration in Ac/Th atoms and s-p migration in Be atoms, similar to the high-pressure behavior of alkaline earth metals. In the past long time, superconductivity and magnetism were considered unable to coexist. However, UBeH8 and NpBeH8 are two potential magnetic superconductors with maximum Tc of 60.70 and 107.18 K at 100 and 350 GPa, respectively, and Hubbard U calculations predict their magnetic moments with 1.52 to 1.90 and 2.49 to 2.92 muB at 0 K. The coexistence of magnetic and superconducting states may be attributed to the different sublattice actions.