COMPUTER-SIMULATION OF DEFECT PRODUCTION BY DISPLACEMENT CASCADES IN METALS

MD simulations of displacement cascades in a variety of pure metals an d alloys of different crystal structure are reviewed. For low recoil e nergies, these simulations have provided extensive results on the orie ntation-dependence and mean value of the displacement threshold energy in different crystal systems, and this information is tabulated. Larg e numbers of recoils have been simulated at true cascade energies, and the results show that Frenkel-pair production at the end of the casca de process is well below the NRT theoretical value in all metals and a lloys. A new empirical relationship between Frenkel-pair number and da mage energy is proposed. In contrast with this, antisite production ef ficiency in ordered alloys increases with increasing energy. Clusterin g of interstitials is a feature of cascade processes for all metals, b ut the degree of clustering is material-dependent. Atomic mixing in ca scades is strongly dependent on cascade energy and is shown to be inde pendent 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.