Superconductivity at ∼100 K in dense SiH4(H2)2 predicted by first principles

Motivated by the potential high-temperature superconductivity in hydrogen-rich materials, the high-pressure structures of SiH4(H-2)(2) in the pressure range 50-300 GPa were extensively explored by using a genetic algorithm. An intriguing layered orthorhombic (Ccca) structure was revealed to be energetically stable above 248 GPa with the inclusion of zero-point energy. The Ccca structure is metallic and composed of hydrogen shared SiH8 dodecahedra layers intercalated by orientationally ordered molecular H-2. Application of the Allen-Dynes modified McMillan equation yields remarkably high superconducting temperatures of 98-107 K at 250 GPa, among the highest values reported so far for phonon-mediated superconductors. Analysis reveals a unique superconducting mechanism that the direct interactions between H-2 and SiH4 molecules at high pressure play the major role in the high superconductivity, while the contribution from H-2 vibrons is minor.