Self-diffusion in a lattice via the interstitialcy mechanism

We study a simple model for the interstitialcy mechanism - one of the main mechanisms of the self-diffusion in crystalline solids. The diffusion coefficient depends on the interstitialcy concentration as well as the hopping rates of particles. We obtain an approximate expressions of the diffusion coefficient for various kinds of lattices by noting that the dynamics of an interstitialcy is identical with that of a particle in the vacancy assisted mechanism. These expressions are found to be consistent with our Monte Carlo simulation results for all the lattices examined as far as the interstitialcy-concentration is not too high.