Abstract

The calculation of materials' properties is not only of scientific interest, but also important for the analysis of experimental findings. Thereby density functional theory (DFT) has become a powerful tool towards the design of solids. Structural properties like lattice parameters, stable phases, ordering phenomena, etc. and the related bonding situation can be predicted very reliably without any adjustable parameter. At the same time, the puzzling situation occurs, that all the state-of-the-art band structure methods are based on DFT, but the band structure calculated that way, does not have a rigorously justified physical meaning. As a consequence, also the parameter-free, i.e., ab-initio, calculation of spectroscopic properties turns out to be a challenge for theoretical and computational physicists. The seminar will provide a guided tour through the basics of some areas, which are the cornerstones in this context: the concept of DFT, optical spectroscopy, and the theoretical approaches, which allow the ab-initio description of spectra. But it will also give an introduction to organic semiconductors, which are top candidates for opto-electronic devices. For these examples it will be shown, how the optical properties can be tuned by computer experiments.