Molecular Crystals and Liquid Crystals, Vol.528, 178-189, 2010
Ordering of a Strong Polar Nematogen (6CBB) in a Dielectric Medium: A Computational Analysis
A computational analysis of molecular ordering of a strongly polar nematogen 4-cyanobiphenyl-4'-hexylbiphenyl carboxylate (6CBB), has been carried out with respect to translational and orientational motions. The atomic net charge and dipole moment at each atomic center have been evaluated using the complete neglect differential overlap (CNDO/2) method. The modified Rayleigh-Schrodinger perturbation theory, along with the multicentered-multipole expansion method, has been employed to evaluate the long-range intermolecular interactions, while the 6-exp potential function has been assumed for short-range interactions. The total interaction energy values obtained through these computations were used as input for calculating the probability of each configuration in a dielectric medium (i.e., noninteracting and nonmesogenic solvent, benzene) at the nematic-isotropic transition temperature (633K) using the Maxwell-Boltzmann formula. On the basis of stacking, in-plane, and terminal interaction energy calculations, all possible geometrical arrangements of molecular pairs have been considered. It has been observed that the energies are redistributed in a dielectric medium, and there is a considerable rise in the probabilities of interactions, although the order of preference remains the same. The present article provides a new and interesting way of looking at the nematogen in a dielectric medium.