SOLUTE-INDUCED EFFECTS ON THE STRUCTURE AND THERMODYNAMICS OF INFINITELY DILUTE MIXTURES

A general molecular-based formalism developed rigorously establishes m icroscopic bases of the supercritical solubility enhancement in terms of well-defined molecular correlation function integrals by unambiguou sly splitting the mixture's properties into short-(finite) and long-ra nge (diverging) contributions. Consequently, the short-range nature of the solute's and solvent's residual chemical potentials is proved and the change of the solvent's local environment around an infinitely di lute solute and its finite contribution to solute mechanical partial m olar properties are interpreted in terms of the short-range solute-sol vent and solvent-solvent direct correlation function integrals. The so lute-induced effect on the system's microstructure and thermodynamics approaches zero as the mixture approaches ideality or the solute becom es an ideal gas particle. At the solvent's critical conditions, the so lute-induced effect on the solute's partial molar properties shows no compressibility-driven singularity, though along the critical isotherm it can exhibit a finite extremum or a change of curvature near critic al density, depending on the type and strength of solute-solvent inter actions. The utility of the proposed solvation formalism is illustrate d using statistical mechanical integral equation calculations for thre e simple models of infinitely dilute near-critical mixtures: pyrene-CO 2, diterbutyl nitroxide-ethane, and Ne-Xe.