Light scattering by nonspherical particles: a refinement to the coupled-dipole method

In the coupled-dipole method an arbitrary particle is modeled as an array of N polarizable subunits, each of which gives rise to only electric dipole radiation. The Clausius-Mosotti relation is widely used to calculate the polarizability of the subunits that correspond to the dielectric function of the particle that the array represents. We replace the Clausius-Mosotti relation with an exact expression for the electric dipole polarizability and find improvement in extinction calculations for spheres as compared with Mie theory. Near a Fröhlich frequency the coupled-dipole method yields extinction cross sections for spheres and spheroids that compare favorably with the continuous distribution of ellipsoids method and measured values.