SIMULATING HIGH-ENERGY CASCADES IN METALS

The processes of radiation damage, from initial defect production to m icrostructure evolution, occur over a wide spectrum of time and size s cales. An understanding of the fundamental aspects of these processes requires a spectrum of theoretical models, each applicable in its own time and distance scales. As elements of this multimodel approach, mol ecular dynamics and binary collision simulations play complementary ro les in the characterization of the primary damage state of high energy collision cascades. Molecular dynamics is needed to describe the indi vidual point defects in the primary damage state with the requisite ph ysical reality. The binary collision approximation is needed to model the gross structure of statistically significant numbers of high energ y cascades. Information provided by both models is needed for connecti ng the defect production in the primary damage state with the appropri ate models of defect diffusion and interaction describing the microstr ucture evolution. Results of binary collision simulations of high ener gy cascade morphology are reviewed. The energy dependence of freely mi grating defect fractions calculated in recent molecular dynamics simul ations are compared to results obtained much earlier with a binary col lision/annealing simulation approach. The favorable agreement demonstr ates the viability of the multi-model approach to defect production in high energy cascades.