Diffusion and Localisation in Random Systems

Direct computer experiments are conducted on electron diffusion in a simple cubic lattice where the disorder corresponds to the Anderson model. Results for the onset of total localisation are in good agreement with other numerical estimates and it is found that the critical value of the parameterW/ZV is (17.7/6). A random structurally disordered system is also investigated with hopping integrals given by V(r) = ‐V0 exp (‐r/a) and found that localisation occurs at the critical value a = 3 ± 0.3. Thisis in agreement with the only other numerical estimate but is substantiallydifferent from theoretical calculations.