A generalized self-consistent mean-field theory for fluids of molecules with distributed polarizabilities: Comparisons with computer simulations

The generalized self-consistent mean field (GSCMF) approximation, recently proposed provides a systematic approach for finding an effective pair poten tial for a fluid of molecules with atom, bond or other distributed polariza bilities. The GSCMF theory is combined with the molecular Ornstein-Zernike (MOZ) theo ry using the hypernetted chain (HNC) approximation to compute the liquid pr operties of polarizable interaction models of water, acetonitrile, and meth anol. The average moments, the excess energies, the dielectric constants, a nd the site-site distribution functions are studied for models with a distr ibuted polarizability or with an overall polarizability at the molecular ce ntre. The MOZ(HNC)/GSCMF results are compared to the data of simulations us ing exact procedures to handle the molecular polarizabilities. Comparison of the results obtained by the MOZ/GSCMF theory and by simulatio ns shows that the MOZ/GSCMF approach correctly predicts the relative change s of the liquid properties caused by a distribution of the polarizability. For the acetonitrile models, the MOZ/GSCMF and simulation results are in, g ood agreement. In contrast for water and methanol, the MOZ/GSCMF theory giv es strongly underestimated total excess energies and average dipoles and th e liquid structure is less pronounced. However, this mainly occurs because the HNC approximation only provides a semi-quantitative description of H bo nding liquids as recently observed for non polarizable models of water and methanol. The results suggest that the GSCMF approach is capable of providing accurat e effective pair potentials for fluids of molecules with distributed polari zabilities. (C) 2000 Elsevier Science B.V. All rights reserved.