Macroscopic dielectric response of the metallic particles embedded in   host dielectric medium
  A theoretical approach is proposed to calculate an effective dielectric constant of a matrix disperse system (MDS) of metallic particles (spheres) randomly distributed and embedded in a uniform dielectric medium. Deviations from the well-known Maxwell Garnett formula have been observed. The effective dielectric constant for different volume fractions of the embedded particles is considered as well as the dependence on pair interaction between particles, and the relation between sizes of each pair of particles. The problem is solved in the electrostatic approximation. 
L.G.Grechko, K.W. Whites, V.N. Pustovit and V.S. Lysenko