Structure and dynamics of silicon-oxygen pairs and their role in silicon self-diffusion in amorphous silica

Abstract

Based on gradient corrected periodic density functional theory calculations, we present the formation, structure, and diffusion of SiO pairs in a-SiO2. We find that a SiO pair preferentially undergoes transformation into an O vacancy through a twofold-coordinated Si atom. We determine the pathways for SiO pair→divalent Si→O vacancy transformation and divalent Si diffusion, along with O vacancy diffusion. Based on these results, we also discuss how the presence of SiO pairs can enhance Si self-diffusion in a-SiO2.