LAUSR

Abstract A quest for room-temperature superconductors is undergoing rapid innovation due to the continuing proliferation of experimental and theoretical researches on high-pressure physics. Hydrogen-caged metal compounds have been proposed to promote high critical temperature superconductivity at pressures, providing a decent opportunity to investigate related phenomena at experimentally attainable pressures. This breakthrough is attributable to the uplifting key parameters, such as electron-phonon interaction and maximum phonon frequency, once thought to be limited, by utilising high pressures. A large class of metal polyhydrides has been theoretically proposed and experimentally realised to promote near-room-temperature superconductivity under high pressures. In this work, we theoretically reported the near-room-temperature superconductivity in a symmetrically M g / C a substituted hexahydride, i.e. M g 0.5 C a 0.5 H 6 . We showed that this ternary M g 0.5 C a 0.5 H 6 compound adopts an I m 3 ¯ m structure, wherein a metal atom is embedded in a H 24 cage, is thermodynamically and dynamically stable at pressures ranging from 200 to 400 GPa. The analyses of the electronic band structure, Fermi surface topologies, phonon dispersion, and spectral function manifest strong support for superconductivity. We obtained λ = 2.53 and ω l o g = 1,400 K for our M g / C a substituted hexahydride at 200 GPa, exhibiting a near-room-temperature T c of 288 K, which completely exceeds the calculated T c of its parent compounds, i.e. M g H 6 and C a H 6 .