Dielectric-constant evaluation from microstructures

We present an accurate, efficient algorithm for calculating the effective d ielectric constant <(epsilon)over bar> of periodic two-component composites with arbitrary unit-cell microstructures. The algorithm is based on a form ulation of the relevant equations in the Bergman-Milton representation of < (epsilon)over bar> that enables the use of the fast Fourier transform in th eir solution, coupled with the sum rules of the geometric spectral function . Our approach accurately reproduces known results, such as the two-dimensi onal checkerboard problem: and yields excellent agreement with experimental ly measured results on random configurations of metallic spheres.