Atomistic study of diffusional mass transport in metals

Rigorous theoretical or phenomenological treatments of microstructure evolu tion in processes such as ageing or irradiaton are based on particular mech anisms of mass transport, i.e. diffusion mechanisms. The information about such mechanisms is usually taken from simple theoretical models derived fro m experimental data. This works well in simple cases, but is limited in com plicated situations like anisotropic diffusion, diffusion in alloys, etc., where the diffusion mechanism is not obvious. In the light of this, the ato mic-scale molecular dynamics (MD) technique is a useful tool for identifyin g and studying actual mechanisms. In this paper we present the results of s tate-of-the-art MD studies applied to diffusional processes in bulk pure me tals. We give a general formulation of the treatment of MD simulations of d iffusion and discuss and compare methods to extract information about parti cular diffusion mechanisms. Examples of calculation of self-diffusion and d efect diffusion coefficients and correlation factors, and treatment of diff usion mechanisms, are given for vacancy and self-interstitial atom diffusio n in fee, bce and hcp metals. The cases of mass transport via small defect clusters (both vacancy and interstitial) are also discussed and examples ar e presented.