The effect of dielectric medium on p-n-decyloxybenzoic acid (10OBAC) at nematic-isotropic transition temperature-A statistical analysis based on computer simulation

The molecular geometry of 10OBAC has been constructed on the basis of the published crystallographic data with the standard values of bond length and bond angles. The evaluation of atomic charge and dipole moment at each atomic centre has been carried out through the Complete Neglect Differential Overlap (CNDO/2) method. The modified Rayleigh-Schrodinger perturbation theory along with multicentred-multipole expansion method has been employed to evaluate long-range interactions while a '6-exp' potential function has been assumed for short-range interactions. The total interaction energy values obtained through these computations were used to calculate the probability of each configuration in dielectric medium (i.e. non-interacting and non-mesogenic solvent, benzene) at room temperature (300 K), nematic-isotropic transition temperature (416 K) and above-transition temperature (450 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. The present article offers a theoretical support to the experimental observations. Also, this provides a new and interesting way of looking at the liquid crystalline molecules in dielectric medium.