In the research group “Theoretical Condensed Matter Spectroscopy” we perform quantum mechanics simulations to predict and understand the properties of complex materials. Modeling the macroscopic properties of a given material on the basis of its microscopic (atomic) structure is a challenging task, which is carried out in two steps. The electronic ground state of the investigated system is modeled in the framework of the density functional theory (DFT). Using it as a starting point, structural and electronic excitations as well as spectroscopic signatures can be calculated. Ab initio molecular dynamics is employed to reproduce the temporal evolution of atomic systems and gain information about phase transitions. Solid state surfaces and interfaces as well as ferroelectrics are our main research topics.