Master Thesis Defense by Amalie Christensen – Niels Bohr Institute - University of Copenhagen

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Niels Bohr Institute > Calendar > NBI Calendar 2014 > Master Thesis Defense ...

Master Thesis Defense by Amalie Christensen

Characterization of defect structures on curved surfaces

A crystal in flat space can in principle be defect free, but this is not the case for a spherical crystal where topology demands a certain number of crystal defects.
In this thesis, the defect structures in periodic phases on a spherical surface is studied using the Phase Field Crystal model.

The triangular phase of the Phase Field Crystal model is used to study grain boundaries terminating freely within the crystal, so called grain boundary scars. The number of dislocations in the grain boundary scars as a function of system size is measured and compared to analytical and experimental results.
The linear relation described by theory and experiment is reproduced by the numerical simulations, but not the slope and intercept.

The defect structure of the striped phase of the Phase Field Crystal model is studied and compared to analytical and numerical predictions for a nematic phase.
Though the Phase Field Crystal model is capable of representing anisotropies through its spatial derivatives, it is not clear whether it can reproduce the essential physics of a nematic phase with an orientational order parameter.