  We present a general approach for the numerical calculation of the effective
dielectric tensor of metamaterials and show that our formalism can be used to
study metamaterials beyond the long wavelength limit. We consider a system
composed of high refractive index cylindric inclusions and show that our method
reproduces the Mie resonant features and photonic band structure obtained from
a multiple scattering approach, hence opening the possibility to study
arbitrarily complex geometries for the design of resonance-based negative
refractive metamaterials at optical wavelengths.
