Browsing by Author "Ambaye, Hailemariam"

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    Diffusion Coefficient of Particles in Lattices with Random-Barriers and wide Distribution of Transition Rates
    (Addis Ababa University, 1995-06) Ambaye, Hailemariam
    We 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=3