Abstract

The continuous time random walk approach for hopping conduction in disordered systems is modified to obtain accurate DC conductivity values over a wide range of hopping site densities. The modification involves eliminating a small fraction of particularly isolated hopping sites from the determination of the waiting-time distribution for hopping. The elimination of these sites does not correspond to a pure truncation in the transition rate spectrum, bur rather a truncation only in the distribution of contributing near-neighbor hopping distances. For a cutoff distance corresponding to the percolation radius r(p), the DC conductivity is within about 1 order of magnitude of percolation-based models and simulation results over a moderate range of hopping site densities. For a slightly larger cutoff distance of 1.15r(p), the DC conductivity is in excellent agreement with the percolation-based theory over a wide range of hopping densities. The introduction of the near-neighbor cutoff does not influence the high-frequency conductivity, where the full CTRW provides an excellent description of the conductivity. Hence, the present simple modification permits an accurate and full interrogation of the frequency-dependent conductivity within a single conceptual framework.

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