Materials Data on Si by Materials Project

Si crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. there are three inequivalent Si sites. In the first Si site, Si is bonded in a tetrahedral geometry to four equivalent Si atoms. All Si–Si bond lengths are 2.82 Å. In the second Si site, Si is bonded to four Si atoms to form corner-sharing SiSi4 tetrahedra. All Si–Si bond lengths are 2.32 Å. In the third Si site, Si is bonded in a distorted see-saw-like geometry to four Si atoms. There are two shorter (2.34 Å) and one longer (2.44 Å) Si–Si bond lengths.