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

Abstract

We present computer simulations of the vapour-nematic interface of the GayBerne model. We considered situations which correspond to either prolate or oblate molecules. We determine the anchoring of the nematic phase and correlate it with the intermolecular potential parameters. On the other hand, we evaluate the surface tension associated to this interface. We find a corresponding states law for the surface tension dependence on the temperature, valid for both prolate and oblate molecules.

A simple predictor of interface orientation of mesogenic fluids and its implications for organic semiconductors

“…For a bulk nematic GB fluid, the orientation at the vapour interface has previously been shown to scale with the ratio of the shape and interaction anisotropy parameters, κ/κ , with a faceon orientation observed for κ/κ < 1, and an side-on orientation otherwise. 36 For the systems studied in this work, in which the bulk phase is isotropic rather than nematic and in which solid interfaces are also considered, Fig. 3 shows that κ/κ is not a good predictor of orientation at either the solid or vapour interface.…”

“…Additional κ values of 0.50 and 0.70 were examined for certain systems to access points with κ > κ, as interfacial behaviour has previously been predicted to exhibit a transition around κ/κ = 1 in some circumstances. 36 Several systems with κ = 1.2 were also studied to examine the behaviour when side-side interactions are stronger than faceface ones. While side-side interactions that are stronger than the face-face ones are not typical of OSCs-like molecules, they can potentially be accessed through, for example, functionalisation of the aromatic core and may present an interesting means of tuning interfacial orientation.…”

“…A smaller subset of these studies have examined the interplay of repulsive and attractive interactions in controlling the interfacial orientation. At a free interface (such as that with a vapour phase), the orientation of anisotropic particles has been studied at various levels, ranging from mean field theories, 33 to particle-based molecular dynamics (MD), 34 and Monte-Carlo (MC) 35,36 simulations. It has been found that switching between the face-on and side-on orientation at this interface can be achieved through tuning the anisotropy of the attractive interactions.…”

“…33 MD simulations of the Gay-Berne (GB) fluid have indicated a dependence of the orientation at the vapour interface of nematic fluids on the ratio of the shape anisotropy to the interaction anisotropy of the particles. 34,36 Fluids that are isotropic in the bulk have also been shown to display preferential alignment at a vapour interface. 35 In contrast, at the solid interface, free volume is maximised in the face-on orientation, for which the long molecular axis is parallel to the interface.…”

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

“…Simulations have been previously reported for GB discotic mesogens focused on tracing changes in phase behavior under confinement [99,130,[136][137][138][139][140] and in droplets [141]. The reader interested in additional parameterizations is referred to previous work [127,129,135,[142][143][144][145][146].…”