Diffusion Coefficient Of Particles In Lattices With Random-barriers And Wide Distribution Of Transition Rates

We have investigated the mean-square displacements of particles that perform randomrnwalks in two and three-dimensional lattices with random barriers with uniformrndistributions of activation energies. The lattice we considered is a mathematical lattice.rnFor the same model Avramov, Milchev, and Argyrakis [phys.rev.E 47 2303 (1993)]rndiscussed the crossover between anomalous and normal diffusion, but they did notrnAnalyze the behavior of the mean-square dispalcements at long times where normalrndiffusion occurs. We point out that the asymptotic diffusion coefficients are wellrndescribed by the effective- medium theory in the range of parameters investigated ; theyrnare in disagreement with the predictions of critical-path arguments in dimension d=3

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