Origin of molecular oxygen formation in irradiated borosilicate glasses studied by molecular dynamics simulation

Abstract

AbstractFormation of molecular oxygen was observed in borosilicate glasses irradiated with energetic ions and electrons, which has significant effects on mechanical properties of glasses and evaluation of High Level nuclear Waste (HLW) immobilization. Though O2 was considered from the broken of X‐O‐Na (X is Si or B) in borosilicate glass, what was X species remained unclear. To find out the original source of molecular oxygen O2 in irradiated borosilicate glasses, several oxygen atoms were artificial randomly removed from the pristine glasses by molecular dynamics simulation (MD). The simulation results suggested that the formation of O2 firstly came from [BO4] units by the conversion of [BO4] to [BO3] units. When the conversion reached saturation, the [SiO4] units acted as the secondary source. Sodium phase separation was also derived after oxygen atoms reduced, which was well‐agreed with electron irradiated glasses. After the oxygen was removed, average Si‐O‐Si angle decreased and the small size rings increased. These simulation results were in good agreement with experiments.