Locally activated Monte Carlo method for long-time-scale simulations

We present a technique for the structural optimization of atom models to st udy long time relaxation pro ceases involving different time scales. The me thod takes advantage of the benefits of both the kinetic Monte Carlo (KMC) and the molecular dynamics simulation techniques. In contrast to ordinary K MC, our method allows for an estimation of a true lower limit for the time scale of a relaxation process. The scheme is fairly general in that neither the typical pathways nor the typical metastable states need to be known pr ior to the simulation. It is independent of the lattice type and the potent ial which describes the atomic interactions. It is adopted to study systems with structural and/or chemical inhomogeneity which makes it particularly useful for studying growth and diffusion processes in a variety of physical systems, including crystalline hulk, amorphous systems, surfaces with adso rbates, fluids, and interfaces. As a simple illustration we apply the local ly activated Monte Carlo to study hydrogen diffusion in diamond.