Ab initio molecular dynamics simulation of low energy radiation responses of α-Al₂O₃

In this study, an ab initio molecular dynamics method is employed to investigate the response behavior of α-Al₂O₃ to low energy irradiation. Different from the previous experiments, our calculations reveal that the displacements of oxygen dominate under electron irradiation and the created defects are mainly oxygen vacancy and interstitial. The experimental observation of the absorption peaks appearing at 203, 233 and 256 nm for α-Al₂O₃ under electron irradiations should be contributed by the oxygen defects and these defects will reduce the transmittance of α-Al₂O₃, which agrees well with the very recent experiment. This study demonstrates the necessity to reinvestigate the threshold displacement energies of α-Al₂O₃, and to introduce recombination center for oxygen defects to improve its optical properties and performance under radiation environment.