ORDERING OF A THERMOTROPIC MESOGEN AT PHASE TRANSITION TEMPERATURE — A STATISTICAL APPROACH BASED ON QUANTUM MECHANICS

Abstract

The molecular ordering of a thermotropic mesogen, 4-alkenyl bicyclohexylnitrile (ALKBCHN), has been carried out on the basis of quantum mechanics and intermolecular forces. The evaluation of atomic charges and dipole moment at each atomic centre has been done through the Complete Neglect Differential Overlap (CNDO/2) method. The configurational energy has been computed using the Rayleigh-Schrodinger perturbation method. The total interaction energy values obtained through these computations were used to calculate the probability of each configuration in a dielectric medium (i.e. non-interacting and non-mesogenic solvent, benzene) at phase transition temperature (364.7 K) using the Maxwell–Boltzmann formula. It has been observed that in dielectric medium the energies/probabilities are redistributed and there is a considerable rise in the probability of interactions, although the order of preference remains the same. An attempt has been made to develop a new and interesting model of mesogen in a dielectric medium. The present article offers a theoretical support to the experimental observations.