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.