Effect of orientational restriction on monolayers of hard ellipsoids

The equilibrium properties of hard rod monolayers are investigated in a lattice model (where position and orientation of a rod are restricted to discrete values) as well as in an off-lattice model featuring spherocylinders with continuous positional and orientational degrees of freedom. Both models are treated using density functional theory and Monte Carlo simulations. Upon increasing the density of rods in the monolayer, there is a continuous ordering of the rods along the monolayer normal ("standing up" transition). The continuous transition also persists in the case of an external potential which favors flat-lying rods in the monolayer. This behavior is found in both the lattice and the continuum models. For the lattice model, we find very good agreement between the results from the specific DFT used (lattice fundamental measure theory) and simulations. The properties of lattice fundamental measure theory are further illustrated by the phase diagrams of bulk hard rods in two and three dimensions. Published by AIP Publishing. [http://dx

show abstract

“…The linearity Q nem ∝ ρ 0 can also be seen in numerical results for a monolayer of ellipsoids [13] (Fig. 4 therein, for an aspect ratio of 10).…”

Section: B Simulationssupporting

confidence: 63%

Monolayers of hard rods on planar substrates. I. Equilibrium

Oettel

Klopotek

Dixit

et al. 2016

The Journal of Chemical Physics

View full text Add to dashboard Cite

show abstract

“…[31][32][33][34][35][36] The studies show there are differences between the nature of 2D nematic ordering and 3D one. So, we examined the orientation ordering properties of 2D hard ellipsoids.…”

Section: Resultsmentioning

confidence: 99%

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

Moradi

Ghotbabadi

Aliabadi

2017

Int. J. Mod. Phys. C

View full text Add to dashboard Cite

The density profiles and corresponding order parameters of the hard ellipsoids confined between two hard walls and also in contact with a single hard wall are studied using the density functional theory. The Hyper-Netted Chain (HNC) approximation is used to write excess grand potential of the system with respect to the bulk value. To simplify the calculations we use restricted orientation model (ROM) for the orientation of ellipsoids to find the density profiles and order parameters. Density functional theory shows that there is a uniaxial-biaxial phase transition near a single hard wall and also between two hard walls for a fluid consisting of uniaxial hard ellipsoidal particles with finite elongation.

show abstract

“…As shown by Monte Carlo simulations and Parsons-Lee density-functional theory, uniaxial freely-rotating plate-like ellipsoidal particles adsorbed on a monolayer without orientational restrictions do exhibit a N b phase, while their rod-like counterparts do not [35]. However it would be necessary to explore a larger variety of particle geometries, without imposing orientational constraints, to finally discard the presence of a biaxial nematic phase.…”

Section: Discussionmentioning

confidence: 99%

Effect of shape biaxiality on the phase behavior of colloidal liquid-crystal monolayers

Gonzalez-Pinto

Martı́nez-Ratón

Velasco

et al. 2015

Phys. Chem. Chem. Phys.

Self Cite

View full text Add to dashboard Cite

We extend our previous work on monolayers of uniaxial particles [J. Chem. Phys. 140, 204906 (2014)] to study the effect of particle biaxiality on the phase behavior of liquid-crystal monolayers.Particles are modelled as board-like hard bodies with three different edge lengths σ 1 ≥ σ 2 ≥ σ 3 , and use is made of the restricted-orientation approximation (Zwanzig model). A density-functional formalism based on the fundamental-measure theory is used to calculate phase diagrams for a wide range of values of the largest aspect ratio (κ 1 = σ 1 /σ 3 ∈ [1, 100]). We find that particle biaxiality in general destabilizes the biaxial nematic phase already present in monolayers of uniaxial particles.While plate-like particles exhibit strong biaxial ordering, rod-like ones with κ 1 > 21.34 exhibit reentrant uniaxial and biaxial phases. As particle geometry is changed from uniaxial-to increasingly biaxial-rod-like, the region of biaxiality is reduced, eventually ending in a critical-end point. For κ 1 > 60, a density gap opens up in which the biaxial nematic phase is stable for any particle biaxiality. Regions of the phase diagram where packing-fraction inversion occurs (i.e. packing fraction is a decreasing function of density) are found. Our results are compared with the recent experimental studies on nematic phases of magnetic nanorods.

show abstract

Effect of orientational restriction on monolayers of hard ellipsoids

Cited by 11 publications

References 62 publications

Monolayers of hard rods on planar substrates. I. Equilibrium

Monolayers of hard rods on planar substrates. I. Equilibrium

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

Effect of shape biaxiality on the phase behavior of colloidal liquid-crystal monolayers

Contact Info

Product

Resources

About