Microstructure and optical properties of random media

I review some of the recent results obtained on the effect of microstructure on the local field distribution and the dielectric constant of a random medium. By using a generalized Onsager approach for the calculation of the local fields, the standard deviation σ of their distribution is found to be directly related to the degree of anisotropy in the local environment of a polarizable particle, and the correction S to the Clausius-Mossotti relation is given by S = σ2. The incorporation of the microstructure in the effective medium and first-principle approaches to the calculation of random media properties is also discussed.