A simplified model for the dielectric function of three-component composite materials

In three-component metal–dielectric composite materials, there are three kinds of metallic particles. Clausius–Mosotti equation is applied to a collection of the three kinds of metallic particles. A simple formula of effective dielectric function for the three-component composite system is derived. The optical absorptive coefficient of Au–Ag–SiO2 composite material is calculated with the derived formula. The calculation predicts the existence of double resonance absorptive peaks, which gives a satisfied explanation of the measured optical absorptive spectra of Au–Ag–SiO2 composite films.