Perturbation theory for nematic liquid crystals of axially symmetric molecules: Numerical results at high pressures including second- and fourth rank orientational order parameters

Abstract

A statistical mechanical perturbation theory is applied to study the thermo-dynamic properties of nematic liquid crystals at the nematic-isotropic (N-I) phase transition under pressure, retaining second- and fourth-rank long-range orientational order parameters. We report calculations for a hard ellipsoidal system superposed with an attractive interaction and subjected to different external pressures. The repulsive interaction is represented by a repulsion between hard ellipsoids characterized by a length-to-width ratio and the interaction arising from the dispersion interaction between two asymmetric molecules represents the attractive interaction. The inclusion of the fourth-rank order parameter in the effective one-body potential ψ(Ω) does not lead to a significant overall improvement. The influence of pressure on the stability, ordering and thermodynamic functions at the N-I transition is analysed. We find that our theoretical predictions are in accordance with experimental observations.