Pressure-induced behavior of the hydrogen-dominant compound SiH4(H2)2 from first-principles calculations

The structural and electronic properties of the high-pressure molecular compound SiH4(H-2)(2) have been calculated using density- functional theory. We identify the molecular hydrogen positions within the face-centered cubic unit cell and further find that pressure-induced intermolecular interaction between SiH4 and H-2 units plays an important role in stabilizing this new compound. The electronic structure is characterized by a wide band gap of 6.1 eV at 6.8 GPa, which closes with pressure and finally becomes metallic at 200 GPa due to electronic band overlap accompanied by a structure change. These findings have potential implications for understanding metallization and superconductivity in H-2.