On disorder-enhanced diffusion in condensed aromatic melts

Disorder-enhanced diffusion of excitations in various aromatic systems can be accounted for by variability of the intersite overlap integrals as has been suggested by Pautmeier et al. (1988, Chem. Phys. Lett., 143, 459) who calculated the ensemble-averaged diffusion coefficient and also carried out computer simulations for diffusing particles. We show that the mathematical problem formulated by Pautmeier et al. allows us to obtain exact solutions in the framework of routine percolation theory. The result drastically differs from that obtained by averaging of local diffusion coefficients and also from the result obtained in previous computer simulations. Reasons for the failure of the averaging procedure are discussed. Model parameters necessary to account for experimental data are determined.