SIMULATING HIGH-ENERGY CASCADES IN METALS

The processes of radiation damage, from initial defect production to microstructure evolution, occur over a wide spectrum of time and size scales. 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, molecular dynamics and binary collision simulations play complementary roles in the characterization of the primary damage state of high energy collision cascades. Molecular dynamics is needed to describe the individual point defects in the primary damage state with the requisite physical reality. The binary collision approximation is needed to model the gross structure of statistically significant numbers of high energy cascades. Information provided by both models is needed for connecting the defect production in the primary damage state with the appropriate models of defect diffusion and interaction describing the microstructure evolution. Results of binary collision simulations of high energy cascade morphology are reviewed. The energy dependence of freely migrating defect fractions calculated in recent molecular dynamics simulations are compared to results obtained much earlier with a binary collision/annealing simulation approach. The favorable agreement demonstrates the viability of the multi-model approach to defect production in high energy cascades.