A molecular dynamics simulation investigation was made of the vacancy-induced densification of silica glass. The equilibration of defective glasses, with various initial concentrations of vacancies, yielded glasses which were denser than the intact glass. The structural and vibrational properties of the densified glasses were characterized. It was found that densification was related to structural changes introduced by atomic rearrangements near to vacancies, and increased with the concentration of vacancies. The vacancies could cluster, and form voids, and the maximum densification for void-structured glasses occurred at a critical radius of about 0.44nm. The glasses densified by vacancies and by simulated ultra-violet laser irradiation exhibited almost identical structural and vibrational properties. The results appeared to support the Douillard–Duraud point defect model as being a common mechanism for the radiation densification of silica glass.

Vacancy-Induced Densification of Silica Glass. Q.An, L.Zheng, S.N.Luo: Journal of Non-Crystalline Solids, 2006, 352[30-31], 3320-5