MONTE-CARLO SIMULATIONS OF ANOMALOUS RELAXATION IN PERCOLATING SYSTEMS

By Monte Carlo simulations of random walks in percolating systems, we show that the anomalous relaxation observed in disordered systems can be ascribed to the restricted geometry allowed for diffusion. In the fractal region corresponding to the concentration p=pc, the relaxation function has scaling properties and becomes the Cole-Cole type, while, in the nonfractal disordered region corresponding to p>pc, the relaxation function becomes the stretched-exponential and Cole-Cole type, respectively, when k2 and k2. From detailed analyses, we give a microscopic explanation for these two types of relaxation functions known so far only as the empirical laws. © 1995 The American Physical Society.