Phase mixing and separation in 2D supramolecular networks

Allen, Alexander (2021) Phase mixing and separation in 2D supramolecular networks. PhD thesis, University of Nottingham.

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Abstract

The study of molecular assemblies through the use of SPM is well documented. This thesis examines assemblies of bi-isonicotinic acid (formally 4,4-dicarboxy-2,2-bipyridine), which forms assemblies that appear to be hydrogen bonded. The interesting element inspiring the study of this molecule is its surface-induced chirality, which restricts certain bonding configurations and orientations.

Experiments were conducted under ultra high vacuum. Both STM and NC-AFM imaging of assemblies were made of the bi-isonicotinic acid molecules deposited on Au(111) and Ag(100). These assemblies were studied at room temperature and using cryogenics, specifically liquid nitrogen and liquid helium. Images showed that the molecules formed organised assemblies with hydrogen bonds locked in a fixed direction. Sub molecular resolution images were also obtained of the networks allowing it to be shown that key bonding site of molecules aligned in an organised manner.

The molecules were then modelled through a set of possible tiles with specific permitted bonding geometries. Monte Carlo simulations were then conducted using algorithms inspired by a heat bath algorithm, which gave considerations to simulated molecules and their translations and rotations with suitable probability weightings. The subsequent behaviour of the molecules was then allowed to evolve under different bond strengths, system temperatures and molecular concentrations. Final state lattices were formed showing different molecular configurations that followed predictable behaviours based on input parameters.

Finally, a study is conducted on the output of the molecular simulations investigating the suitability of machine learning in predicting both initial input parameters of a system, and also its ability to categorise final state configurations in both objective and subjective classifications. While results for objective classifications were almost definitively predicted, a correlation was also observed between the subjective classifications, particularly between those that are most similar to each other.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Moriarty, Philip J
O'Shea, James
Keywords: Phase mixing, 2D supramolecular networks
Subjects: Q Science > QC Physics > QC170 Atomic physics. Constitution and properties of matter
Faculties/Schools: UK Campuses > Faculty of Science > School of Physics and Astronomy
Item ID: 66977
Depositing User: Allen, Alexander
Date Deposited: 12 Dec 2021 04:40
Last Modified: 12 Dec 2021 04:40
URI: http://eprints.nottingham.ac.uk/id/eprint/66977

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