Computational discovery of a dynamically stable cubic SH3 -like high-temperature superconductor at 100 GPa via CH4 intercalation

The 203 K superconductivity of ${\mathrm{SH}}_{3}$ stimulates enormous interest in searching for high-temperature superconductors in compressed hydrides. While several hydrides show high-temperature superconductivity ($>180\phantom{\rule{0.16em}{0ex}}\mathrm{K}$) 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 ${\mathrm{CSH}}_{7}$ that can be viewed as methane (${\mathrm{CH}}_{4}$) molecules inserted into the ${\mathrm{SH}}_{3}$ host lattice as a guest. Ionic bonding in this special host-guest arrangement acts as a chemical precompression for ${\mathrm{SH}}_{3}$, leading to a much lower predicted dynamically stable pressure of 100 GPa for ${\mathrm{CSH}}_{7}$ than that of ${\mathrm{SH}}_{3}$ at 170 GPa. Given the superhigh superconductivity of the parent ${\mathrm{SH}}_{3}$ sublattice, we performed electron-phonon coupling calculations to estimate the ${T}_{c}$ of ${\mathrm{CSH}}_{7}$ 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.