Influence of the intermolecular electrostatic potential on properties of polar polarizable aprotic solvents

The liquid properties of models of acetonitrile, acetone and chloroform are calculated within the framework of the hypernetted chain approximation of the molecular Ornstein-Zernike theory. The shape of a molecule is described by a set of Lennard-Jones sites. Its electrostatic properties are modelled either by the first multipole moments up to the octopole or by partial cha rges, and by a point polarizability tensor. The multipole moments and the p artial charges are computed by ab initio molecular orbital methods. In the liquid phase, the polarizability is taken into account by calculating an ef fective induced point dipole moment using a self-consistent mean-field appr oximation. While the Lennard-Jones part of the internal excess energy is ne arly independent of the description of the electrostatic interaction and of the polarizability, the electrostatic part and the dielectric constant cha nge notably. The models with the partial charges lead to dielectric constan ts which are in good agreement with the experimental data, provided that th e molecular polarizability is correctly taken into account. The internal ex cess energies are also correctly predicted except for acetone. How the appr oximation of the intermolecular electrostatic interaction modifies the liqu id structure is studied by investigating the dominant bimolecular configura tions. These configurations allow one to understand better why the Kirkwood factor changes with the electrostatic description. The Ornstein-Zernike fo rmalism is a practical tool for studying with light numerical effort how th e liquid properties depend on the intermolecular interaction. It can help i n the development of new accurate potentials for liquid simulation.