Defect cluster formation in displacement cascades in copper

Extensive study of primary damage in displacement cascades in metals by computer simulation has shown that the total number of defects produced is significantly lower than predicted by the Norgett, Robinson and Torrens (NRT) model and that a significant fraction of the self-interstitials forms glissile clusters. However, there is a lack of variety of defect types observed in cascade simulation, which, in many cases, makes it difficult to explain experimental data. For example, experiments on copper show efficient production of stacking fault tetrahedra (SFTs) but they were not observed systematically in computer simulation. To consider this further, extensive simulation of displacement cascades in copper has been performed using two different interatomic potentials, a short-range many-body potential (MBP) and a long-range pair potential (PP). Primary knock-on-atom (PKA) energy in the range 2-20 keV and temperatures of 100 and 600 K were considered. Special attention was paid to cascade statistics and the accuracy of simulation in the collision stage. The former required many simulations for each energy whereas the latter involved a modification of the simulation method to treat a hot region with high accuracy by applying a smaller time step. Results showing the variety of clusters observed, e.g. SFTs, glissile and sessile interstitial clusters, and faulted and perfect interstitial dislocation loops, are presented.