Diffusion in a system of impurity centers with dipole-dipole hopping rates

Random walks in disordered media with dipole-dipole transition rates are considered. The long-time asymptotics of the process are investigated on the basis of a new numerical simulation method, which includes periodic continuation of the system without periodic continuation of the initial condition. It is shown that the long-time asymptotics have a diffusive character. The concentration dependence of the diffusion coefficient for simple cubic and face-centered cubic lattices is studied. (C) 1998 American Institute of Physics. [S1063-7761(98)02012-5].