PUB - Publikationen an der Universität Bielefeld

This thesis is about the determination of the structure of carbon nanosheets with the help of the classical EDIP potential. Such layers are produced at the Bielefeld University in an experimental physics working group. The manufacturing process includes irradiating the layers with electrons. As a result, the molecules are dehydrated and cross-linked with each other so that they become mechanically stable. First tests are carried out to investigate, whether the structure of the carbon nanosheets can be determined with the EDIP potential after the electron irradiation.

For this purpose, an observable is required which, on the one hand, can be calculated in theory and, on the other hand, can be measured in experiments. There is not so much choice of observables. For example, one could think of conductivity as an observable. It is wonderfully measurable in the experiment. However, the theoretical model used cannot determine conductivity. Conversely, one could calculate a lot in theory. This would require special equipment for the experiment, which is likely to be expensive. In this thesis, the Young's modulus is used as an observable.

The first step is to find structures whose Young's modulus match the theory and experiment. A structural analysis can then be carried out in the second step. The first step is not entirely trivial. This is very computationally intensive as it depends on many grid parameters. In this thesis methods for reducing the computational complexity are presented and the overall optimization problem is formulated.

The first calculations show a very interesting behaviour. It was investigated how the Young's modulus and the structure of carbon nanosheets depend on the randomization and the distance between the molecules. These trends have been characterised.