Effective Dielectric Response of Composites Containing Uniaxial Inclusions

An approach is proposed for the calculation of an effective dielectric function for a composite medium containing randomly oriented particles with uniaxial polarisability (the medium is isotropic on average). A scalar renormalised average polarisability of the particles is introduced, which takes complete account of the tensor nature of the dipole–dipole interaction between them. Fluctuations originating from their random positions are treated in the spirit of the average T-matrix approximation. The renormalised polarisability is related to the effective dielectric function via the Maxwell-Garnett equation. The theory is illustrated by calculating the reflectivity and absorption of a colloidal solution of hexagonal CdS particles.