Menu

*p* and surface grand potential Θ_{ s }of system of hard-rods near a hard wall are derived. The system is studied in the nonlocal version of Onsager low-density approximation. Θ_{ s }, the equilibrium density and the nematic order parameter profiles at the bulk nematic-isotropic coexistence are calculated. The nonlocal approximation is shown to satisfy the pressure sum rule. From the behaviour of the profiles we conclude that the geometrical packing effects manifest themselves most strongly in the density profile and rather weakly in the order parameter profiles.

*x*, while for HE and HSC the nematic density at the transition exceeds the close packing density in some range of *x*, around *x* = 1. Also the dependence on *x* of the nematic order parameter, *Q*, the density, Δη, and entropy, Δ*S*, jumps at N–I transition is completely different for HC in comparison to HE and HSC.

*R* are studied in the context of the Sullivan model. Neither a first nor a continuous transition is found for finite *R*. Only in the strict limit of *R*→∞ a second-order transition appears. For temperatures *T* higher than the wetting temperature in a flat geometry, *T*^{∞}_{w}, the thickness *l* of the enhanced density layer, which forms on the surface of the sphere, is for large *R* proportional to In *R*.

*–*isotropic-phase coexistence are considered. It is found that the angle between the director and the normal to the interface is approximately 60° and does not depend on the length-to-width ratio *L/D* of the spherocylinder. The nematic-phase*–*isotropic-phase surface tension, however, tends linearly to zero as *D/L→0*. It is also argued that the anisotropic hard-core repulsion favors the perpendicular alignment at the nematic free surface. The results concerning the tilt angle are in good agreement with experimental studies for *n*CB (*n=5*,*6*,*7*,*8*) [(4-*n*-alkyl-4’-cyano)biphenyl].

*Q* is enhanced near the wall even though the density is reduced. The wall-induced biaxiality *P* is small in the interfacial region. We find that wetting by the nematic phase should occur at the nematic-isotropic coexistence.

_{ t }*and* increases the order parameter *Q*. We show that in the case of perfect alignment (*Q* = 1) the nematic-wall surface tension (γ) does not have the usual form of a polynomial in cos^{2} ϑ_{ t }. Using a simple local approximation for the one-particle distribution function we find an analytical expression for γ(ϑ_{ t }) for the system of hard cylinders and also calculate γ(ϑ_{ t }) numerically for the system of hard spherocylinders.

**66**, 3667 (1977)] that the wetting layer, which forms on a spherical surface, always has a finite thickness l∼lnR where R is the radius of a sphere. The temperature Tw of a first-order wetting transition is higher in a spherical geometry than in a flat one. The shift of the transition temperature Tw is proportional to lnR/R for large R.