Simulation of interstitial diffusion in an amorphous structure

The authors investigate the random walk of an interstitial atom through an amorphous structure. The interaction between the diffusing particle and the atoms in the matrix is defined through a model potential which can be used in any disordered material and has strong interrelations with the corresponding Voronoi network. The stochastic process is carefully described as consisting of two random walks: one on the net of interstitial sites, the other on the time axis. Thus, the authors can perform a Monte-Carlo experiment on a simulated amorphous sample. They show that the concept of percolation greatly reduces the complexity of the problem: one can define a percolation threshold for the saddle points, such that only those which are near to this value need be considered. Numerical results are obtained which show the gaussian character of the motion. Finally, the diffusion coefficient is evaluated and shown to be a little higher than in crystalline materials.