Coarse-grained kinetic Monte Carlo simulation of diffusion in alloys

We present a coarse-grained Monte Carlo method designed for the simulation of vacancy-mediated diffusion phenomena. A coarse-grained master equation is derived from the atomic scale master equation using an assumption of local equilibrium within each coarse-grained cell. Atomic kinetic Monte Carlo (AKMC) simulations are used to perform both the thermodynamic and the kinetic parametrization of the coarse-grained simulations. Quantitative reproduction of flux couplings is achieved in the coarse-grained simulation. The ability of the CKMC method to simulate kinetics controlled by diffusion such as a precipitate dissolution and the decay of sinusoidal modulations of the concentration field is illustrated on body-centered-cubic (bcc) model alloys with a clustering tendency. It is shown on the case of a model of the Fe-Cu alloy previously developed that the use of this method can reduce the computational cost of a kinetic simulation by several orders of magnitude.