Superconducting Be2SH3 with kagome hydrogen at high pressure

Compressed hydrides containing diverse hydrogen motifs usually exhibit desirable properties, such as superconductivity. Here, we show that hydrogen atoms form an intriguing kagome lattice in the Be-S-H system, which is superconducting below megabar pressures. Using first-principles crystal structure prediction methods, a hitherto unknown stoichiometry Be2SH3 is identified to be thermodynamically stable above 168 GPa and can remain dynamically stable down to 60 GPa. Interestingly, the H atoms in Be2SH3 are arranged to form a kagome sublattice, and S atoms occupy Be hexagon centers. Further calculations show that Be2SH3 is superconducting with T-c of 29 K at 100 GPa, which originates mainly from the coupling between the electrons of S atoms as well as H-kagome, and the low phonon frequencies dominated by in-plane Be-vibrations and out-of-plane S-vibrations. Besides, the contribution of the H-kagome lattice to the total electron-phonon coupling increases linearly with pressure, indicating its enhanced role in the superconductivity under pressure.