Displacement Cascades. Dynamics and Atomic Structure

The seminal ideas of Seeger, in 1958 and 1962, on the nature of a displacement cascade (DC) in irradiated crystalline materials have played an important role in the field of radiation damage. This paper first reviews the early history of displacement spikes, replacement collision sequences (RCSs), “diluted” or depleted zones and thermal spikes. Then the use is discussed of molecular dynamics (MD) simulations and field‐ion microscopy as techniques by which one can study the dynamics of the formation of DCs and the spatial array of point defects — on an atomic scale — associated with quiescent DCs, respectively. These techniques demonstrate quantitatively that a DC consists of a vacancy‐rich core surrounded by a distribution of self‐interstitial atoms (SIAs) — the latter are predominately created by RCSs. Recent results on the application of MD to the behavior of 5 keV cascades in copper are presented. Some of the results of the application of field‐ion microscopy to the study of DCs in tungsten are reviewed, and compared with the MD results.