Radiation-induced glide motion of interstitial clusters in concentrated alloys

We propose a mechanism for glide motion, i.e. one-dimensional (1D) migration, of interstitial clusters in concentrated alloys driven by high-energy particle irradiation. Interstitial clusters are fundamentally mobile on their respective 1D migration tracks, but in concentrated random alloys they are stationary at the position where the fluctuating formation energy achieves a local minimum. Irradiation changes the microscopic distribution of solute atoms through atomic displacement and recovery of the produced Frenkel pairs, which causes cluster 1D migration into a new stable position. In molecular dynamics simulations of interstitial clusters up to 217i in Fe–Cu alloys, stepwise 1D migration was observed under interatomic mixing or shrinkage of the cluster: a single 1D migration was induced by two exchanges per atom or cluster radius change by two interatomic distances. The 1D migration distance ranged up to several nanometers. We compared the frequency and distance of 1D migration with those for in situ observation using high-voltage electron microscopy, allowing for the extremely large rate of interatomic mixing and cluster shrinkage in the present simulation.