Bulk electronic structure of SiO₂

The electronic structures of crystalline and amorphous SiO₂ are examined via the tight-binding method. A new tight-binding Hamiltonian, fit to experiment and to the pseudopotential band structure of α quartz, is used to calculate densities of states for both α quartz and an SiO₂ Bethe lattice. These are shown to compare favorably with x-ray photoemission spectra of α quartz and amorphous SiO₂. The computational results are analyzed qualitatively using the bond-orbital approach. For both crystalline and amorphous SiO₂ it is suggested that oxygen 2s character in the lower conduction bands may be necessary to account for the large gap. Local symmetries of the lone-pair-like bands of possible relevance to the optical properties are discussed.