Stability and mobility of small vacancy and copper-vacancy clusters in bcc-Fe: An atomistic kinetic Monte Carlo study

The mobility and the stability of small vacancy (V) and copper-vacancy (Cu-V) clusters play a key role in the microstructural evolution of Fe–Cu alloys under irradiation, but these are largely unknown parameters that cannot be experimentally measured. These parameters have therefore been determined using atomistic kinetic Monte Carlo (AKMC) simulations, where the vacancy jump activation energies as functions of the local atomic environment had been previously calculated using a molecular dynamics (MD) code and tabulated for use in the AKMC code. This method allowed relaxation effects to be implicitly included in the model and possible differences between the predictions of different interatomic potentials to be evaluated. In this work the mobility, lifetime and mean free path of clusters containing up to six vacancies and Cu-V complexes containing up to four components has been studied. In the case of the VV and Cu-V pairs, the results obtained with different many-body potentials are compared with ab initio results. All results are briefly discussed in terms of their impact on the microstructure evolution in irradiated FeCu alloys.