Nina Krapf

Master Thesis (current)

• Under the supervision of Simon Grabowsky at the University of Bern.
• Working title: "Controlling Measurement Errors in Experimental Wavefunctions"

Bachelor Thesis

• Completed in May 2025 under the supervision of Simon Grabowsky at the University of Bern.
• Title: "How Different Can Water Be? A Computational, Quantum-Crystallographic, and Statistical Analysis"

My Bachelor thesis focused on the investigation of the geometry of water in crystalline hydrates deposited in the CSD. The distribution of covalent O--H bond lengths in these water molecules demonstrates a significant discrepancy between the structures measured using Neutron Diffraction, and those determined by X-Ray Diffraction, as X-ray data shows an artificially shortened mean covalent bond length in comparison to neutron structures. The reason for this disagreement was found in the standard refinement model, the Independent Atom Model, which systematically underestimates X-H bond lengths, and in the use of the riding model with fixed hydrogen atom positions. It was estimated that 180,000 of the 210,000 hydrate structures in the CSD may contain incorrect bond parameters, and require re-refinement using Hirshfeld Atom Refinement. The broad shape of the H--O--H bond angle distribution in both datasets was attributed to the low energetic penalty associated with bond angle deformation in water molecules, as indicated by a potential energy scan. In the crystalline environment, such small energy costs may be compensated by favourable intermolecular interactions.