Phase equilibria, fluid structure, and diffusivity of a discotic liquid crystal

Abstract

Molecular Dynamics simulations were performed for the Gay-Berne discotic fluid parameterized by GB(0.345, 0.2, 1.0, 2.0). The volumetric phase diagram exhibits isotropic (IL), nematic (ND), and two columnar phases characterized by radial distribution functions: the transversal fluid structure varies between a hexagonal columnar (CD) phase (at higher temperatures and pressures) and a rectangular columnar (CO) phase (at lower temperatures and pressures). The slab-wise analysis of fluid dynamics suggests the formation of grain-boundary defects in the CO phase. Longitudinal fluid structure is highly periodic with narrow peaks for the CO phase, suggestive of a near-crystalline (yet diffusive) system, but is only short-ranged for the CD phase. The IL phase does not exhibit anisotropic diffusion. Transversal diffusion is more favorable in the ND phase at all times, but only favorable at short times for the columnar phases. In the columnar phases, a crossover occurs where longitudinal diffusion is favored over transversal diffusion at intermediate-to-long timescales. The anomalous diffusivity is pronounced in both columnar phases, with three identifiable contributions: (a) the rattling of discogens within a transient "interdigitation" cage, (b) the hopping of discogens across columns, and (c) the drifting motion of discogens along the orientation of the director.

Computer simulation study of the nematic–vapour interface in the Gay–Berne model

“…Finally, we are not aware of any study which considers the nematic-vapour coexistence for oblate molecules. Discotic liquid crystals stand for promising materials for technological applications [31] and they have been recently studied by using Gay-Berne [32,33] and related models such as the Gay-Berne-Kihara model [34,35].…”

Toward Transferable Coarse‐Grained Potentials for Poly‐Aromatic Hydrocarbons: A Force Matching Approach

“…In the absence of intramolecular (out of plane) vibrations, the columnar phase becomes more stable in the CG system, unlike the atomistic case. The stacked and T‐shape configurations are marked by the first peak and a subsequent shoulder in the atomistic RDF of coronene. The ill‐resolved shoulders in the corresponding CG RDF suggest that these two different configurations could not be resolved further at the CG level, owing to the larger size of the planar CG coronene molecule.…”

A Bidimensional Gay-Berne Calamitic Fluid: Structure and Phase Behavior in Bulk and Strongly Confined Systems

“…The GB model uses four parameters conventionally represented as GB(κ, κ ′ , μ, ]). Previous work has shown that specific parameter sets reproduce thermodynamic and structural properties of experimental systems [105,107,127]. A complete phase diagram of the 3D GB model is available for GB(3, 5, 2, 1) [104,[128][129][130][131][132], which corresponds to a calamitic mesogen.…”

“…Several GB parameterizations have reproduced nematic and smectic phases [102][103][104]. More recently, a discotic parameterization has been used to explore nematic and columnar phases [105][106][107][108][109], providing insight on structural and dynamic measurements at the molecular level [110][111][112]. The recognition of specific design principles has stimulated the attainment of novel targets [27].…”