The atomic structure and structural stability of neutral O vacancies on amorphous silica were investigated by using combined Monte Carlo and density functional calculations. It was found that, unlike the bulk counterparts, the Si-Si dimer configuration of surface O vacancies was likely to be unstable due to the high tensile strains induced, thus encouraging thermally activated transformation (over a moderate barrier) into other stable configurations including di-coordinated Si, silanone, or a sub-surface Si-Si dimer; depending upon the local surface structure. Pathways for the interconversion between these O-vacancy related defects were proposed.

Structure and Interconversion of Oxygen-Vacancy-Related Defects on Amorphous Silica. C.L.Kuo, G.S.Hwang: Physical Review Letters, 2006, 97[6], 066101 (3pp)