Computer simulation of topological defects around a colloidal particle or droplet dispersed in a nematic host

Abstract

We use molecular dynamics to study the ordering of a nematic liquid crystal around a spherical particle or droplet. Homeotropic boundary conditions and strong anchoring create a hedgehog (radial point defect) director configuration on the particle surface and in its vicinity; this topological defect is canceled by nearby defect structures in the surrounding liquid crystal, so as to give a uniform director field at large distances. We observe three defect structures for different particle sizes: a quadrupolar one with a ring defect surrounding the particle in the equatorial plane; a dipolar one with a satellite defect at the north or south pole; and a transitional, nonequatorial, ring defect. These observations are broadly consistent with the predictions of the simplest elastic theory. By studying density and order-parameter maps, we are able to examine behavior near the particle surface, and in the disclination core region, where the elastic theory is inapplicable. Despite the relatively small scale of the inhomogeneities in our systems, the simple theory gives reasonably accurate predictions of the variation of defect position with particle size.

Interactions between spherical colloids mediated by a liquid crystal: A molecular simulation and mesoscale study

“…Systems of LCs and one or two colloids have been studied by experimental, 4 -8 simulation, [9][10][11][12][13][14] and theoretical methods [15][16][17][18][19][20][21][22][23][24] in connection with their associated defect structures and effective interactions. The simplest case corresponds to a single spherical colloid embedded in a nematic fluid, with strong homeotropic ͑perpendicular͒ anchoring at the colloid surface.…”

Potential of mean force between a spherical particle suspended in a nematic liquid crystal and a substrate

“…This potential has been employed in a previous study of a colloidal particle in a bulk liquid crystal, 6 and is known to reproduce topological defects around the particle that are in agreement with theory and experiment. The force on a sphere is calculated as the derivative of the interaction potential between the liquid crystal and the sphere with respect to z; due to symmetry in the (x,y) plane, only the z component of the force contributes.…”

“…[3][4][5] Colloidal particles in liquid crystals have also been studied by computer simulations. 6,7 One of the questions that arises from these experiments pertains to the nature of the liquid-crystal-mediated interaction between the colloids, or a colloidal particle and a surface.…”

Effect of substrate geometry on liquid-crystal-mediated nanocylinder-substrate interactions

“…Molecular simulation has been used to study LC structure around single nanoparticles [18][19][20][21] and interactions between small numbers of them [22][23][24] , but for larger systems becomes prohibitively expensive.…”