Surface phenomena are an integral part of everyday life -- whether in the appearance of bubbles in the sink after washing one's hands or in the design of water-repellent clothing. Surface phenomena also find application in industrial processes, such as catalysis, fluid purification, or separation. For industrial application, materials with huge surface-to-volume ratios are preferred. Solids with pores in the nanometer range (i.e. nanoporous solids) are such materials, and of these, metal-organic frameworks are the most versatile class. Metal-organic frameworks have already received a high level of attention. The modular structure -- MOFs consist of inorganic nodal building blocks that are connected by organic linking building blocks -- allows almost continuous adjustment of pore size, shape, and environment. However, many aspects of surface phenomena in or on metal-organic frameworks are not yet fully understood. For example, it is known that entropy favors the accumulation of smaller guest molecules in nanoporous solids at high loading. But does entropy also favor the accumulation of water in metal-organic frameworks with internal hydrophobicity? Speaking of which, how is the hydrophobicity of the internal and external surface of metal-organic frameworks related? And how can modern visualization techniques, such as virtual reality, help in studying metal-organic frameworks and the guest molecules within them? This thesis aims to shed light on these questions using classical molecular simulations. Molecular simulations are a helpful tool for studying surface phenomena, because they can complement experiments by providing insights at the microscopic level, and offer the possibility of exploring surface phenomena that can only rarely be investigated in experiments, plus help to improve the efficiency of experiments by predicting metal-organic frameworks with desired properties.

Hybridstrukturen aus organischen und anorganischen Halbleitern (HIOS) vereinen die besten Eigenschaften beider Materialklassen zu Konjugaten mit großem Anwendungspotential. Ihre engen Struktur-Eigenschafts-Beziehungen, eröffnen viele interessante wissenschaftliche Herausforderungen. Um z.B. ihre optoelektronischen Eigenschaften vorherzusagen, müssen die früher Stadien des Dünnschichtwachstums erforscht werden. Das erste Ziel dieser Arbeit ist es, den Einfluss der Entropie auf die Oberflächendiffusion von kurzen Polyphenyl Molekülen auf amorphem Siliziumdioxid, a-SiO2 zu untersuchen. Das zweite Ziel ist es, den Einfluss partieller Fluorierung auf para-Sexiphenyls (p-6P) zu untersuchen. Des Weiteren untersuchen wir Selbstdiffusion von p-6P auf einer Zinkoxid (ZnO) Oberfläche und Selbstorganisation bzw. Schichtwachstum auf a-SiO2. Hierfür verwenden wir klassische atomistische Molekular- und Langevin-Dynamik-Simulationen, kombiniert mit klassischer Diffusionstheorie. In Bezug auf das erste Ziel quantifizieren wir die entropischen Beiträge zu den Freie-Energie-Barrieren für die Oberflächendiffusion von Polyphenylen unterschiedlicher Länge und zeigen, dass die Entropie zum dominierenden Teil der freien Energie für längere Moleküle wird. Zweitens demonstrieren wir, dass die Erhöhung der Anzahl fluorierter Gruppen im p-6P die Diffusion in der apolaren Richtung der ZnO-Oberfläche verringert, aber die Diffusion in der polaren Richtung erhöht. Drittens untersuchen wir den Einfluss der Fluorierung auf die Nukleation und das Wachstum von p-6P auf a-SiO2 mit einem Simulationsmodell, das experimentelle Gasphasenepitaxie nachahmt. Wir reproduzieren korrekte Einheitszellen bei Raumtemperatur und zeigen, dass die Erhöhung der Anzahl fluorierter Gruppen zu einem Schicht-für-Schicht-Wachstum auf der Oberfläche führt. Diese Arbeit ebnet den Weg für zukünftige Simulationen von Dünnschichtwachstum kleiner organischer Moleküle auf anorganischen Oberflächen. / Hybrid structures of organic molecules and inorganic semiconductors (HIOS) combine favorable properties of each material into conjugates with great application potential. The optoelectronic properties of hybrid materials depend on the structure of individual molecules and their alignment relative to the inorganic surface. It is an interesting scientific challenge to predict the optoelectronic properties of HIOS based on studying the early stages of thin film growth and interface formation. The aim of this thesis is to investigate the effect of entropy in surface diffusion of short polyphenyl molecules on an amorphous silicon dioxide, a-SiO2. Second objective is to study the influence of partial fluorination of the organic para-sexiphenyl molecule (p-6P) on self-diffusion on an inorganic zinc oxide (ZnO) surface and on self-assembly and growth on the a-SiO2. For this we employ all-atom molecular dynamics and Langevin dynamics simulations, combined with classical diffusion theory. In respect to the first aim, we quantify entropic contributions to the free energy barrier of surface diffusion for short oligophenyls of varying length and demonstrate that entropy becomes even the dominant part of the free energy for longer molecules. For the second aim, we demonstrate that the increase in the number of fluorinated groups inside of the p-6P decreases the diffusivity in the apolar direction of the ZnO surface but increases the diffusivity in the polar direction. Thirdly, we study the influence of fluorination on nucleation and growth on a-SiO2 with a simulation model that mimics experimental deposition from the vapor. We reproduce the structures with correct room-temperature unit-cell parameters and demonstrate that the increase in the number of fluorinated groups leads to a layer-by-layer growth on the surface. This work can stimulate ideas for future simulations of nucleation and growth of small organic molecules with high tuning potential, on inorganic surfaces.