A perturbation theory for solvation thermodynamics: Dipolar-quadrupolar liquids

The thermodynamics of solvation of a dipole in hard sphere solvents with dipoles and quadrupoles is studied by using the Pade approximation for the perturbation expansion of the solvation chemical potential and compared to Monte Carlo simulations. Solvation chemical potentials, energies, and entropies of solvation are obtained at different dipolar and quadrupolar solvent strengths. The effect of nonlinear solvation is analyzed and found not to exceed 10% in the parameter range studied. An agreement between the simulations and the analytical theory is obtained by an empirical rescaling of the triple perturbation integrals of the perturbation expansion. This rescaling does not, however, provide a quantitatively correct partitioning of the solvation free energy into the energy and entropy of solvation. (C) 1999 American Institute of Physics. [S0021-9606(99)51531-6].