Theory of amorphous SiO2andSiOx. II. Electron states in an intrinsic glass

With the use of a continuous-random-network type of structural model with periodic boundary conditions, the electronic structure of an intrinsic glass is calculated by applying a first-principles method. Results are presented for the density of states (DOS), partial DOS, localization index of one-electron wave functions, and effective atomic charges. Detailed correlations are made between the calculated electronic structures and the local structural distortions present in the network models. No localized electron states are found near the conduction-band edge. The localized states at the valence-band edge are traced to the bond-elongated atoms. A mobility edge of about 0.2 eV is estimated for the top valence band of amorphous Si${\mathrm{O}}_2$.