Ab initio determination of basic dielectric properties

Simulating the performance of fibre optical devices or photonic devices requires an accurate solution of Maxwell´s equations. However, the resulting predictions often depend quite crucially on the knowledge of the basic dielectric constants within certain frequency ranges, where experimental data could be very inaccurate or simply not available. We illustrate the theoretical and numerical background to work out frequency dependent dielectric constants using modern ab initio methods based on density functional theory. The starting point will be a rough picture of the atomic structure of a given dielectric component. We discuss various technical aspects to determine the electronic and ionic parts of the dielectric constant for a given frequency range, and we give some illustrative examples.