Computational NMR studies in carbon nanostructures

Nuclear magnetic resonance (NMR) is a technique that makes it possible to probe the inside of materials and study what kind of environment the atoms experience.

In this thesis, the change in NMR signals when carbon atoms or xenon gas are placed in different nanometre-scale environments is investigated. This is done computationally, by combining quantum-mechanical calculations with atomistic simulations. This approach serves as a computer-based NMR laboratory, where conditions can be controlled precisely and phenomena that are hard to separate in real experiments can be studied in detail.

Here, carbon-based nanostructures, such as spherical fullerenes and tube-like carbon nanotubes were studied. These are promising materials for future electronics and gas storage, but their behaviour is difficult to measure and interpret using experiments alone.

The first part focuses on the fullerene molecule C₆₀, made of 60 carbon atoms arranged like a football. The results show that this molecule can behave in an unusual way when heated: it contracts before it starts to expand. The second and third parts deal with xenon gas inside and around carbon nanotubes. The calculations reveal that the NMR signal is highly sensitive to whether xenon is inside a tube, on its outer surface, or in the narrow gaps between tubes, and also to whether a nanotube is electrically metallic or semiconducting. These findings suggest that xenon could be used as a probe to detect the surrounding nanostructure, with the NMR signal acting as a sensitive indicator of tube structure and electronic properties.

Overall, the thesis demonstrates that carefully designed computational methods can clarify puzzling experimental NMR observations and deepen our understanding of carbon nanomaterials. This knowledge supports future research on new applications and on more accurate techniques for measuring and modelling nanostructured materials.