The formation of vacancy-type defect clusters by ion bombardment: A problem revisited by molecular dynamics

In 1969 Professor Balluffi and students L. E. Thomas and T. Schober presented a series of three papers on the nature of defects produced by keV Au irradiation of Au [Thomas et al., Radiat. Effects 1, 257, 269, 279 (1969)]. They noted that vacancy clusters were produced with high efficiencies but could not find evidence for interstitial clusters. The authors interpreted their data on the basis of replacement collision sequences carrying interstitial atoms beyond the cascade core, leaving behind a vacancy rich depleted zone which subsequently collapsed into a visible dislocation loop. We have simulated this experiment by molecular dynamics and can now predict much of what these authors reported in 1969. However, 25 years later we offer a new explanation for the creation of vacancy clusters based on viscous flow of liquid metal through the irradiated surface.