Confinement of interstitial cluster diffusion by oversized solute atoms

We study the effects of oversized solute atoms on the diffusion of clusters of self–interstitial atoms produced in metals by high–energy irradiation. We use kinetic Monte Carlo (KMC) simulations in model body–centred cubic iron, and include elastic interactions between the defects. We show that elastic repulsion between solute atoms and the clusters can confine the latter to one–dimensional segments. The easy direction of motion of each cluster is assumed to rotate infrequently, allowing it to escape to a new confined segment. The consequences of the confinement for the effective diffusivity of the cluster and its rate of reaction with other small static spherical sinks are explored both by KMC simulations and by an analytic theory. It is shown that the predictions of the theory agree very well with the computer simulations. We suggest some of the possible consequences of these findings for the design of alloys that are more resistant to the effects of high–energy radiation damage.