Topological and bonding defects in vitreous silica surfaces

Abstract

A model structure for an annealedsilicasurface was obtained through the molecular dynamics simulation technique employing three‐body interaction potentials. Nonbridging oxygen and edge‐sharing tetrahedra were found to form on the oxygen‐terminated surface with three‐coordinated silicon, three‐coordinated oxygen, and three‐membered rings just below the outermost atoms. Four‐membered rings were also created in relatively large concentrations during the surface relaxation. When considering the effect of removing periodic boundary conditions along the z direction, the concentration of larger rings, relative to the bulk, remained unchanged throughout the ∼11 Å simulated surface region. A strong physical association between three‐membered rings and three‐coordinated oxygen was found which may account for the D 2 defect peak observed in Raman scattering.