Comparison of algorithms for multiscale modelling of radiation damage in Fe-Cu alloys

A key issue for the simulation of radiation effects in reactor pressure vessel (RPV) steels is the kinetics of formation of Cu-vacancy complexes (Cu-VC) in a ferritic matrix, starting from displacement cascade debris. In the present work the evolution of molecular dynamics (MD) and corresponding binary collision approximation (BCA) displacement cascades has been studied using two different kinetic Monte Carlo (KMC) techniques in Fe-0.2% Cu. This exercise allows an assessment of the cascade debris features that are likely to influence their long-term evolution in interaction with the solute atoms, as well as the differences between simulation techniques. The results show that, at the current level of approximation of KMC methods, the use of BCA as damage input in KMC simulations does not introduce major biases, the difference with respect to the use of an MD source being a second-order effect. This justifies the use of BCA cascade debris as input damage for KMC parametric studies of Cu precipitation in Fe under irradiation, with a view to increasing the statistical representativity of the results. The main open question remains the mobility and dissociation rate of small Cu-VC, as described with different KMC techniques.