Pressure-induced superconducting CSH with an HS framework.

The discovery of the high-temperature superconducting state in the compounds of hydrogen, carbon and sulfur with a critical temperature () of 288 K at high pressure is an important milestone towards room-temperature superconductors. Here, we have extensively investigated the high-pressure phases of CSH, and found four phases 2, 31, 3̄1 and . Among them, 31 can be dynamically stable at a pressure as low as 50 GPa, and 2 has a high of 155 K at 150 GPa. Both 2 and 31 are host-guest hydrides, in which CH molecules are inserted into 3̄-HS and 3-HS sublattices, respectively. Their is dominated by the HS lattice inside. The insertion of CH molecules greatly reduces the pressure required for the stability of the original HS lattice, but it has a negative impact on superconductivity which cannot be ignored. By studying the effect of CH insertion in the HS lattice, we can design hydrides with a close to that of HS and a greatly reduced pressure required for stability.