First-principle study of the structural, electronic and optical properties of defected amorphous silica

Abstract

The oxygen-excess structures include oxygen dangling bond, peroxy linkage (POL), peroxy radical (POR) and interstitial oxygen molecule or ozone molecule defects, while the oxygen-deficient structures include neutral oxygen vacancy, E′ center and oxygen double-bond. For both the undefected and the various defected structures, the electronic and optical properties are calculated by plane-wave pseudo potential density functional theory. The oxygen-deficient defected structures lead to the remarkable increases in the density of states (DOS) at the top of valence band and near the bottom of the conduction band. The oxygen-excess defected structures change the distribution of defect levels and there appear new levels between the valence band and conduction band. All the defects lead to the increase of static dielectric constants and the enhancing absorption in the low energy range. Absorption peaks can be observed below 2eV for NBOHC defected structures. Though the energy loss is generated at the lower energy region, the loss strength below 2eV for oxygen-excess defected structures is stronger than oxygen-deficient defected structures. During the calculation the dangling bond in the structures are neutralized by hydrogen atoms. This work may give insights into the laser induced damage towards to vitreous silica.