Real space calculation of optical constants from optical to x-ray frequencies

We present a theory of linear optical constants based on the single-particle density operator and implemented in an extension of the real space multiple scattering code known as FEFF. This approach avoids the need to compute wave functions explicitly and yields efficient calculations for frequencies ranging from the IR to hard x-rays, which is applicable to arbitrary aperiodic systems. The approach is illustrated with calculations of optical properties and applications for several materials and compared with existing tabulations.