High-pressure crystal structures and superconductivity of Stannane (SnH4)

摘要

There is great interest in the exploration of hydrogen-rich compounds upon strong compression where they can become superconductors. Stannane (SnH4) has been proposed to be a potential high-temperature superconductor under pressure, but its high-pressure crystal structures, fundamental for the understanding of superconductivity, remain unsolved. Using an ab initio evolutionary algorithm for crystal structure prediction, we propose the existence of two unique high-pressure metallic phases having space groups Ama2 and P63/mmc, which both contain hexagonal layers of Sn atoms and semimolecular (perhydride) H2 units. Enthalpy calculations reveal that the Ama2 and P63/mmc structures are stable at 96–180 GPa and above 180 GPa, respectively, while below 96 GPa SnH4 is unstable with respect to elemental decomposition. The application of the Allen-Dynes modified McMillan equation reveals high superconducting temperatures of 15–22 K for the Ama2 phase at 120 GPa and 52–62 K for the P63/mmc phase at 200 GPa.