Superconductivity of novel tin hydrides (Sn${}_n$H${}_m$) under pressure

With the motivation of discovering high-temperature superconductors, evolutionary algorithm is employed to search for all stable compounds in the Sn-H system. In addition to the traditional SnH${}_4$, new hydrides SnH${}_8$, SnH${}_{12}$ and SnH${}_{14}$ are found to be thermodynamically stable at high pressure. Dynamical stability and superconductivity of tin-hydrides are systematically investigated. I$\bar{4}$m2-SnH${}_8$, C2/m-SnH${}_{12}$ and C2/m-SnH${}_{14}$ exhibit higher superconducting transition temperatures of 81, 93 and 97 K compared to the traditional compound SnH${}_4$ with T${}_c$ of 52 K at 200 GPa. An interesting bent H${}_3^{-}$ in I$\bar{4}$m2-SnH${}_8$ and novel liner H${}_4^{-}$ in C2/m-SnH${}_{12}$ are observed. All the new tin-hydrides remain metallic over their predicted range of stability. The intermediate-frequency wagging and bending vibrations have more contribution to electron-phonon coupling parameter than high-frequency stretching vibrations of H${}_2$ and H${}_3$.