Perturbation theory for fluids of non-spherical polarizable dipolar molecules

Abstract

Wertheim's renormalized thermodynamic perturbation theory is extended to systems of the polarizable dipolar Kihara molecules and applied to the polarizable dipolar two-centre Lennard-Jones (LJ) fluid. In the third-order perturbation theory, the thermodynamic properties of the reference two-centre LJ fluids are evaluated via the thermodynamic functions of the corresponding system of the Kihara rod-like molecules. For the molecular distribution function of the Kihara fluid the function of the corresponding Gaussian overlap model is substituted. From the second- and third-order perturbation terms (determined for the permanent dipole moment and constant isotropic polarizability) the Padé approximant is formulated and its derivative used for the determination of the value of the effective dipole moment. The final value of the effective dipole moment is used to evaluate the electrostatic contributions to the residual Helmholtz energy, pressure and internal energy. For the given value of the permanent dipole moment the thermodynamic functions depend both on polarizability and elongation of the model considered (and on temperature and density). Fair agreement of the theoretical results with simulation data for the polarizable Stockmayer and polarizable dipolar 2cLJ fluids was found.