Bounds for the effective dielectric constant of disordered two-phase materials

Derives upper and lower bounds for the effective dielectric constant epsilon * of a disordered medium in which the local dielectric constant can take one of two values epsilon 1 and epsilon 2 and which on the average is uniform and isotropic. To derive the bounds the author uses Bergman's analytic representation (1978, 1981) of epsilon * as a complex function of epsilon 1 and epsilon 2. The bounds are expressed in terms of the three-point correlation function of the medium and are identical with Kroner's optimum third-order bounds when these are applied to the present situation. For certain types of material the upper and lower bounds coincide and epsilon * is given exactly by the Clausius-Mossotti expression.