Abstract
A model is presented that determines the effect of oxygen and helium on the energies of the common vacancy-cluster configurations, namely the void, dislocation loop and stacking-fault tetrahedron. Representative calculations are given for the case of irradiated copper. The presence of oxygen tends to enhance the stability of the void during nucleation compared to the other vacancy-cluster morphologies by decreasing the void surface energy through a chemisorption process. Helium also tends to stabilize void formation, because of the high binding energy of helium to a vacancy (or cluster of vacancies) compared to a dislocation. Gas concentrations as low as 0·01 a.p.p.m. He and 5 a.p.p.m. O are predicted to stabilize void formation in copper at certain temperatures. The predictions of the model are in good agreement with the available experimental results.
