The role of Cu in displacement cascades examined by molecular dynamics

Molecular dynamics simulations of displacement cascades in pure Fe, Fe–0.2 at.% Cu and Fe–2 at.% Cu have been done with different primary knocked-on atom (PKA) energies. The typical defects (vacancies and interstitials) appear during the cascade process. Most of the defects recombine in the first few picoseconds. The presence of Cu atoms does not seem to influence the primary damage in the time span covered by MD. Neither Cu precipitates, nor dilute atmospheres have been observed to form in the course of the MD simulations. However, a tendency to form mixed objects (vacancies or interstitials gathered with Cu atoms) is noticed in the Fe–2 at.% Cu. Our feeling is that the numerous vacancies left at the end of the cascade recombination phase will interact with the Cu atoms and will act as attractive centers. The role of the interstitials is less clear for the moment.