Showing papers by "Shri Singh published in 1983"

Perturbation Theory for Nematic Liquid Crystals of Axially Symmetric Molecules: II. Effect of Quadrupolar Forces

Abstract: A statistical mechanical perturbation theory, that derives from the work of Singh and Singh, is applied to analyse the influence of quadrupole interaction on a variety of thermodynamic properties of nematic liquid crystals. Numerical evaluations are done for a model system in which molecules are assumed to interact via a pair potential having both repulsive and attractive parts. The repulsive interaction is represented by a repulsion between hard spherocylinders. The attractive potential, a function of only the centre of mass distance and the relative orientation between the two molecules, is represented approximately by the isotropic dispersion and anisotropic quadrupole interaction between two asymmetric molecules. The properties of the reference system and the first order perturbation term are calculated by assuming that an angle-dependent range parameter scales the pair correlation function such that it decouples the orientational degrees of freedom from the translational one. The functional ...

Perturbation theory for non-axial molecular fluids

Abstract: The thermodynamic perturbation theory in which all angle-dependent interactions are considered as a perturbation of the central potential is applied to study the equilibrium properties of a fluid composed of non-axial molecules. The influence of a large number of anisotropic pair and three-body non-additive interactions have been taken into account. Using the same set of force parameters the calculation is made for gaseous pressure second and third virial coefficients and liquid phase thermodynamic properties (Helmholtz free-energy, configurational energy, pressure and entropy). It is shown that the non-axial approximation is an improvement over the axial one. Excellent agreement between theory and experiment is obtained for ethylene.