Density functional theory of liquid crystals and surface anchoring

Abstract

This paper applies the density functional theory to confined liquid crystals comprising ellipsoidal shaped particles interacting through the hard Gaussian overlap (HGO) potential. The restricted orientation model proposed by Rickayzen [Mol. Phys. 95, 393 (1998)] is extended to study the surface anchoring. The excess free energy is calculated as a functional expansion of density around a reference homogeneous fluid. The pair direct correlation function (DCF) of a homogeneous HGO fluid is approximated, based on the Percus-Yevick DCF for hard spheres; the anisotropy is introduced by means of the closest approach parameter. The average number density and orientational order parameter profiles of a HGO fluid confined in between planar walls are obtained using a hard needle-wall potential to represent the particle-wall interactions. For short and long needle lengths, the homeotropic and planar anchoring are observed, respectively. For the bulk isotropic phase the calculated density and order parameter profiles are in agreement with the Monte Carlo simulation of Barmes and Cleaver [Phys. Rev. E 69, 61705 (2004)]. However, for the bulk nematic phase the theory gives the correct density profile between the walls. The correct order parameters are obtained close to the walls whereas for the region in the middle of the walls, the agreement is less satisfactory.

The study of uniaxial–biaxial phase transition of confined hard ellipsoids using density functional theory

“…To understand the physical properties of the different states of matter, various theoretical methods like integral equations 1 and molecular dynamics 2 have been used. One of the most successful theories is the density functional theory (DFT) which has been proven to be a powerful tool in the study of the thermodynamics and structures of the bulk and non-uniform phases of the molecular fluids [3][4][5] . It has been applied to examine, nuclei, atoms, molecules, solids and the quantum and classical fluids.…”

“…One of the most successful theories is the density functional theory (DFT) which has been proven to be a powerful tool in the study of the thermodynamics and structures of the bulk and non-uniform phases of the molecular fluids [3][4][5] . It has been applied to examine, nuclei, atoms, molecules, solids and the quantum and classical fluids.…”

Orientational ordering of confined hard rods: The effect of shape anisotropy on surface ordering and capillary nematization

“…For example, the walls can give rise to different anchoring phenomena and result in various phase behaviors like a shift in the phase transition with respect to that of the bulk phase [6,7]. In general, when a liquid is located in contact with another phase, like a solid surface, the substrate gives rise to substantial changes in the structure and the phase behavior of the liquid [8,9]. This is because of the strong competition between particle-particle (intrinsic interactions) and particle-substrate (extrinsic interactions) interactions [10].…”

Confinement Induced Ordering in Fluid of Hard Ellipsoids

“…Teixeira et al [26] carried out a simulation study of the effects of nanoconfinement on a system of hard Gaussian overlap particles. These studies lead to the conclusion [27][28][29][30][31][32] that various particle shape and confinement have remarkable effects on the configurations of fluid.…”