Deterministic simulations of the rate equations governing cluster dynamics in materials are limited by the number of equations to integrate. Stochastic simulations are limited by the high frequency of certain events. We propose a coupling method combining deterministic and stochastic approaches. It allows handling different time scale phenomena for cluster dynamics. This method, based on a splitting of the dynamics, is generic and we highlight two different hybrid deterministic/stochastic methods. These coupling schemes are highly parallelizable and specifically designed to treat large size cluster problems. The proof of concept is made on a simple model of vacancy clustering under thermal ageing.

The microstructure evolution in irradiated materials can be conveniently modelled, at large scale, by cluster dynamics (CD). In this approach, the effect of the local environment of defect clusters is neglected. In this article, we first check the validity of this assumption by comparing CD to object kinetic Monte Carlo (OKMC) simulations. We show that for microstructures produced under irradiation, taking into account in CD only the average dependency of clusters' growth rate on volume fraction does not permit to reproduce reference OKMC results. Accordingly, the sink strength dispersion, quantified using OKMC, is introduced in CD, using a new formalism depending on the Voronoi volumes of defect clusters. CD calculations including sink strength dispersion are shown to be in better agreement with reference OKMC simulations and experimental observations than are classical CD calculations.