Simulation of the atomic collision cascade

Abstract

Molecular dynamics computer simulations can be used to evaluate pre-existing theorttical concepts, or used directly as a research tool, simulations can directly investigate natural phenomena. The TRIM program, a binary-collision simulation of atomic collision cascades, is a well-known example of the first usage. This paper compares and contrasts TRIM results with computations from a multiple-interaction cascade simulation program, QDYN. QDYN is described in detail; then some issues of potential function development for simulation use are introduced, followed by some examples of QDYN based research. Two current simulation based research topics are presented in greater detail. One is a study of very low energy cascades, where directed bonds and chemical effects are important. The other is the influence of electronic processes on cascade development. Characteristics of atoms ejected from the surface are emphasised. Both topics have potential applications in the simulation of atomic collision cascades in insulators. These investigations emphasise the possibility that direct comparisons between simulations of collision cascades in metals, semiconductors, and insulators can help to solve outstanding research problems in both fields.