Modelling Cluster Structures and Properties at Different Length Scales

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A new spectrally broad band white light emitter based on adamantane-like cluster material has been discovered. This material in combination with cheap, low-power continuous-wave infrared laser diodes has the potential to be used in high-brilliance applications. The first investigated cluster material [(StySn)4S6] consists of a tin-sulfide-based adamantane-like core saturated with organic styrene ligands. Investigations of clusters with modified adamantane core composition and different organic ligands suggest that a disorder in the macroscopic structure is required to generate white light. Furthermore, another nonlinear optical effect, namely the second harmonic generation of the fundamental laser light, was found for clusters that show no white light generation. The recent studies demonstrate the need to understand the structural and electronic features of the cluster material as well as the underlying nonlinear optical effects in order to design and fine-tuning cluster materials to the desired properties. This theoretical research project will focus on the calculation and modelling of the geometric structures of single clusters up to solid state material and related electronic and vibrational properties. Therefore, numerous variations of the cluster core and the organic ligands will be considered. The project will closely collaborate with the theoretical project of C2 (Sanna) which focuses on the modelling of the nonlinear optical effects and all experimental groups of the research group. The systematic study of single clusters and small cluster agglomerates will allow to identify trends in structure and properties of white light or second harmonic generating clusters. Based on the understanding of the fundamental structural features of the cluster interaction, modeling of amorphous-like solid state cluster structures will contribute to the understanding of short- and long-range order in the cluster material as well as its manipulation. The study will answer the question how the cluster interaction can be influenced by cluster composition. The calculation of the cluster material at different length scales connected to each other will allow structural and property-related insights beneficial to an optimization for desired nonlinear optical effects.