CORRELATION AND MULTIPOLAR EFFECTS IN THE DIELECTRIC RESPONSE OF PARTICULATE MATTER - AN ITERATIVE MEAN-FIELD THEORY

A systematic approach for treating correlations and multipolar effects in particulate matter is proposed. The method consists of an iterative extension of the Maxwell-Garnett (MG) mean-field approach. The first iterate beyond MG that involves up to three-particle correlations is solved fully to all multipolar orders using Kirkwood's superposition approximation and yields a simple improved formula for the composite dielectric constant at low filling. We find that at 5% filling resonances that originate in multipolar couplings carry about 6% of the total strength. Our results reproduce accurately low-density measurements on pure argon.