Showing papers by "Shri Singh published in 1984"

Perturbation Theory for Nematic Liquid Crystals of Axially Symmetric Molecules: Extension of Calculations to High Pressures

Abstract: We have applied a statistical mechanical perturbation theory to study the thermodynamic properties of nematic liquid crystals under pressure. In this theory the reference potential function is nonspherical and consists of the short range rapidly varying repulsive part of the pair potential. We report calculations on the nematic-isotropic (NI) transition properties for a hard spherocylindrical system superposed with an attractive potential, which is a function of only the centre of mass distance and the relative orientation between the two molecules, and subjected to different external pressures. The interaction arising from dispersion interaction between two asymmetric molecules represents the attractive interaction. The influence of pressure on the stability, ordering and thermodynamic functions for the NI transition is analysed. It is found that the theoretical predictions are in accordance with the experimental observations.

Anisotropic screening in polar fluids and the extent of its accommodation by molecular perturbation theories that use sphericalized reference states

Abstract: We developed a function that is sensitive to many‐body screening of the anisotropy in dense molecular fluids and applied it to dipolar fluids and to ST2 water. For these fluids, the function was found to be oscillatory with distance and to become damped, for dipolar fluids, with increasing strength of the dipole moment. We then compared this function to the screening implied by the Gray–Gubbins and RAM reference state potentials. For ST2 water these comparisons suggested that a composite potential made up of equal proportions of the RAM and the Gray–Gubbins potential might be better than either the RAM or the Gray–Gubbins potentials alone.