Superconductivity of novel tin hydrides (SnnHm) under pressure

With the motivation of discovering high-temperature superconductors, evolutionary algorithm USPEX is employed to search for all stable compounds in the Sn-H system. In addition to the traditional SnH₄, new hydrides SnH₈, SnH₁₂ and SnH₁₄ are found to be thermodynamically stable at high pressure. Dynamical stability and superconductivity of tin hydrides are systematically investigated. Im2-SnH₈, C2/m-SnH₁₂ and C2/m-SnH₁₄ exhibit higher superconducting transition temperatures of 81, 93 and 97 K compared to the traditional compound SnH4 with Tc of 52 K at 200 GPa. An interesting bent H₃-group in Im2-SnH₈ and novel linear H in C2/m-SnH₁₂ 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 H2 and H3.