Dielectric and structural results for liquid acetonitrile, acetone and chloroform from the hypernetted chain molecular integral equation

This paper reports an attempt to model pure liquids of polar polarizable molecules of arbitrary symmetry and to compute their structural properties in a simple, rapid but fairly accurate way. The models consist of approximating each molecule as a superposition of Lennard-Jones sites with a centred point polarizable electric dipole and a point electric quadrupole. The calculation of the liquid structure is performed using the hypernetted-chain approximation, in which the solvent polarizability is treated at the self-consistent mean-field level. The quadrupole moments are measured or obtained by ab-initio molecular orbital calculations. The orientational correlations between the molecules, as measured by the Kirkwood g factor, and the dielectric constants are mainly determined by the molecular shapes, sizes and electrostatic interactions but are nearly independent of the Lennard-Jones attraction. The theoretical values of the dielectric constants are in satisfactory agreement with the experimental data, provided that both the effects of the quadrupole moment and of the polarizability are incorporated in the electrostatic intermolecular potential. The liquid structure is presented by the dominant configurations found between two molecules. The Kirkwood g factor is correlated to these configurations.