The effects of one-dimensional glide on the reaction kinetics of interstitial clusters

Collision cascades in metals produce small interstitial clusters and perfec t dislocation loops that glide in thermally activated one-dimensional (1D) random walks. These gliding defects can change their Burgers vectors by the rmal activation or by interactions with other defects. Their migration is t herefore 'mixed 1D/3D migration' along a 3D path consisting of 1D segments, The defect reaction kinetics under mixed 1D/3D diffusion are different fro m pure 1D diffusion and pure 3D diffusion, both of which can be formulated within analytical rate theory models of microstructure evolution under irra diation. Atomic-scale kinetic Monte Carlo (kMC) defect migration simulation s are used to investigate the effects of mixed 1D/3D migration on defect re action kinetics as a guide for implementing mixed 1D/3D migration into the analytical rate theory. The functional dependence of the sink strength on t he size and concentration of sinks under mixed 1D/3D migration is shown to lie between that for pure 1D and pure 3D migration and varies with L, the a verage distance between direction changes of the gliding defects. It is sho wn that the sink strength in simulations for spherical sinks of radius R un der mixed 1D/3D migration for values of L greater than R can be approximate d by an expression that varies directly as R-2. For small L, the form of th e transition from mixed 1D/3D to pure 3D diffusion as L decreases is demons trated in the simulations, the results of which can be used in the future d evelopment of an analytical expression describing this transition region. ( C) 2000 Elsevier Science B.V. All rights reserved.