Humpert, Anja (2016) Computer simulations of liquid crystals. PhD thesis, University of Warwick.

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Abstract

In this thesis we studied nematic liquid crystals using molecular dynamics simulations based on the coarse grained Gay-Berne potential. The elastic and dynamical properties of the nematic bulk were calculated and the impact of the system size and simulation run time were investigated showing that both have to be considered carefully. For the bend fluctuations we observed propagating modes for the director and velocity components. This contradicts statements found in the literature that assume these modes are overdamped. We derive from nematodynamics that this assumption may not be valid for all systems and hence we argue that propagating modes may be observed in experiments.

Furthermore we studied defect structures forming due to nanoparticle inclusions in nematics. Depending on the particle size and the surface anchoring three different defect types were observed: Saturn ring, surface-ring and boojum defects. The satellite defect was found to be unstable for the particle sizes studied here, which is in agreement with theoretical predictions. For two nanoparticles in close proximity entangled defects formed, similar to experimental observations for micron sized particles. We explain the three-ring structure, which was observed in other molecular simulations, as a superposition of the different entangled states.

Finally we calculated the line tension and viscous drag of a single disclination line of strength -1/2. Nanoparticles placed in close proximity of the single disclination experienced highly non-linear attractive forces. Once the particle ‘touches’ the disclination it remained connected for the entire simulation. In addition we have shown that the presence of a single disclination has a significant impact on inter-nanoparticle interactions.

Item Type:	Thesis or Dissertation (PhD)
Subjects:	Q Science > QC Physics
Library of Congress Subject Headings (LCSH):	Liquid crystals -- Computer simulation
Official Date:	August 2016
Dates:	Date Event August 2016 Submitted
Institution:	University of Warwick
Theses Department:	Department of Physics
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Allen, Mike
Sponsors:	Engineering and Physical Sciences Research Council
Extent:	x, 143 leaves : illustrations, charts
Language:	eng

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