Essen, Universiẗat, Diss., 2005--Duisburg.

This work presents excited state investigations on several systems with respect to experimental spectroscopic work. The majority of projects covers the temporal evolution of excitations in thin films of organic semiconductor materials. In the first chapters, thinfilm and interface systems are build from diindeno[1,2,3-cd:1’,2’,3’-lm]perylene (DIP) and N,N’-bis-(2-ethylhexyl)-dicyanoperylene-3,4:9,10-bis(dicarboximide) (PDIR-CN2) layers, in the third chapter bulk systems consist of 4,4’,4”-tris[(3-methylphenyl)phenylamino] triphenylamine (m-MTDATA), 4,7-diphenyl-1,10-phenanthroline (BPhen) and tris-(2,4,6-trimethyl-3-(pyridin-3-yl)phenyl)borane (3TPYMB). These were investigated by aggregate-based calculations. Careful selection of methods and incorporation of geometrical relaxation and environmental effects allows for a precise energetical assignment of excitations. The biggest issue was a proper description of charge-transfer excitations, which was resolved by the application of ionization potential tuning on aggregates. Subsequent characterization of excitations and their interplay condenses the picture. Therefore, we could assign important features of the experimental spectroscopic data and explain differences between systems. The last chapter in this work covers the analysis of single molecule spectroscopy on methylbismut. This poses different challenges for computations, such as multi-reference character of low-lying excitations and an intrinsic need for a relativistic description. We resolved this by combining complete active space self-consistent field based methods with scalarrelativistic density-functional theory. Thus we were able to confidently assign the spectroscopic features and explain underlying processes. / Im ersten Teil dieser Arbeit (Referenz [4]) wurden Anregungen in DIP und PDIR-CN2 Aggregaten berechnet und charakterisiert, um Signale experimenteller TR-SHG Spek- tren zuzuweisen und zugrundeliegende Prozesse aufzuklären. Der Fokus des ersten Ka- pitels liegt auf der zeitlichen Entwicklung der Populationen der angeregten Zusände in den individuellen Materialien. Diese Anregungen haben Frenkel Charakter und konn- ten deswegen mit standard RS-Funktionalen beschrieben werden. Die Umgebung wur- de durch atomare Punktladungen modelliert. Absoptionsspektren konnten zugewiesen werden, allerdings mit einer systematischen Abweichung in den Anregungsenergien. Diese Zuweisung wurde diskutiert mit Blick auf Größe der untersuchten Aggregate, Relaxationseffekte und den Funktional-inherenten Fehler. Die Signale in den TR-SHG Spektren wurden hauptächlich auf Aggregateffekte zurückgeführt. Dazu gehören (De- )Lokalisierungsprozesse, Population von tiefliegenden Fallenzuständen und Relaxation zum Grundzustand. Zusätzlich konnten wir Vibrationsprogressionen durch Schwingun- gen der Monomere erklären ...

In this thesis we have investigated the correlated ground state properties of polymers by applying wave-function-based ab-initio quantum-chemical methods such as the Hartree-Fock approach, the full configuration interaction method (FCI), coupled-cluster (CC) and Moller-Plesset second-order perturbation (MP2) theory. The polymers we have studied are the boron-nitrogen polymers, i.e., polyiminoborane (PIB) and polyaminoborane (PAB), the lithium hydride chain and the beryllium hydride polymer as well as the polymethineimine (PMI). The optimized structural parameters, cohesive energies, polymerization ernergies, relative stabilities of isomeric forms and some band structure results are presented. The results demonstrated that quantum chemical ab initio methods can be applied successfully to infinite systems like polymers, although such calculations are still far from being routine.

Stuttgart, Univ., Diss., 2008.

Stuttgart, Univ., Diss., 2007.

Zugl.: Düsseldorf, Univ., Diss., 2007 u.d.T.: Graf, Martin: Dichtefunktionalrechnungen zur homogenen Katalyse mit Übergangsmetallen / Hergestellt on demand

Stuttgart, Univ., Diss., 2002.

Stuttgart, Univ., Diplomarb., 2003.

Stuttgart, Univ., Diss., 2004.

Stuttgart, Univ., Diss., 2005.