Microscopic Calculation of Localized Electron States in an Intrinsic Glass

A microscopic calculation of localized electron states of an intrinsic, real, threedimensional disordered solid has been attempted by applying a first-principles method to a structurally relaxed large network of amorphous silicon dioxide. A valence-band mobility edge of 0.15-0.30 eV is estimated. No localized states are found near the conduction-band edge. The nature and the microscopic origin of these localized states are analyzed in terms of local structural disorder.