Electronic, Vibrational, and Superconducting Properties of High-Pressure Metallic SiH₄: ab initio Calculations

We extensively explore the experimentally proposed metallic structure of hcp P6₃ for the hydrogen rich compound, SiH₄. It is found that the lattice dynamic of this structure is severely unstable. By freezing the soften mode, an orthorhombic Pbcn structure is discovered to be dynamically stable up to 226GPa. Within the conventional BCS theory, the calculated critical temperature T_c within the proposed Pbcn structure is 16.5K at 188GPa, in good agreement with the experimental result (17.5K). Thus, we propose that the current predicted orthorhombic phase is a better candidate for the metallic phase of SiH₄.