Computer simulation of defect production by displacement cascades in metals

Abstract

MD simulations of displacement cascades in a variety of pure metals and alloys of different crystal structure are reviewed. For low recoil energies, these simulations have provided extensive results on the orientation-dependence and mean value of the displacement threshold energy in different crystal systems, and this information is tabulated. Large numbers of recoils have been simulated at true cascade energies, and the results show that Frenkel-pair production at the end of the cascade process is well below the NRT theoretical value in all metals and alloys. A new empirical relationship between Frenkel-pair number and damage energy is proposed. In contrast with this, antisite production efficiency in ordered alloys increases with increasing energy. Clustering of interstitials is a feature of cascade processes for all metals, but the degree of clustering is material-dependent. Atomic mixing in cascades is strongly dependent on cascade energy and is shown to be independent of crystal structure. The mechanisms underlying these results are discussed, particularly in relation to the highly disordered zone formed at the end of the thermal spike.