Calculating the complex permittivity of powdered crystalline material at infrared and terahertz frequencies

In this paper we calculate the complex permittivity of a crystalline material supported in a non-absorbing medium. To do this we have developed a software package, PDielec, which post processes solid state quantum mechanical and molecular mechanical calculations of the phonons and dielectric response of the crystalline material. Using an effective medium approximation, the package calculates the internal electric field arising from different particle morphologies and calculates the resulting shift in absorption frequency and intensity arising from the coupling between each phonon mode and the resultant internal field.