Computational Discovery Of A Dynamically Stable Cubic Sh3-Like High-Temperature Superconductor At 100 Gpa Via Ch4 Intercalation

The 203 K superconductivity of SH3 stimulates enormous interest in searching for high-temperature superconductors in compressed hydrides. While several hydrides show high-temperature superconductivity (>180 K) at extremely high pressure, it is highly desired to design hydrides that can achieve similar superconductivity at relatively lower pressure. In this work we identify a cubic structure in ternary CSH7 that can be viewed as methane (CH4) molecules inserted into the SH3 host lattice as a guest. Ionic bonding in this special host-guest arrangement acts as a chemical precompression for SH3, leading to a much lower predicted dynamically stable pressure of 100 GPa for CSH7 than that of SH3 at 170 GPa. Given the superhigh superconductivity of the parent SH3 sublattice, we performed electron-phonon coupling calculations to estimate the T-c of CSH7 at high pressure, which could reach 181 K at 100 GPa. Our results may shed light on the design principle for other multinary host-guest high-temperature superconducting hydrides with low stable pressure.