Ambaye, Hailemariam2018-06-272023-11-092018-06-272023-11-091995-06http://10.90.10.223:4000/handle/123456789/3817We have investigated the mean-square displacements of particles that perform random walks in two and three-dimensional lattices with random barriers with uniform distributions of activation energies. The lattice we considered is a mathematical lattice. For the same model Avramov, Milchev, and Argyrakis [phys.rev.E 47 2303 (1993)] discussed the crossover between anomalous and normal diffusion, but they did not Analyze the behavior of the mean-square dispalcements at long times where normal diffusion occurs. We point out that the asymptotic diffusion coefficients are well described by the effective- medium theory in the range of parameters investigated ; they are in disagreement with the predictions of critical-path arguments in dimension d=3enLattices with Random-BarriersThesis