Some recent developments in the statistical mechanical theory of ionic solvation
| Autor: | J. M. G. Barthel, H. Krienke |
|---|---|
| Rok vydání: | 1994 |
| Předmět: | |
| Zdroj: | Pure and Applied Chemistry. 66:405-410 |
| ISSN: | 1365-3075 0033-4545 |
| DOI: | 10.1351/pac199466030405 |
| Popis: | Solvation forces in electrolyte solutions may advantageously be treated with sta- tistical mechanical methods from a unique point of view on the Born-Oppenheimer (BO) level. Integral equation techniques of the RNNC type are used and the potentials of mean force and the correlation functions yielding the excess functions are estimated for typical model solvents such as nonpolar and polar hard spheres or Lennard-Jones particles etc. The solvation contri- butions (Gurney potentials) to the effective interactions are presented and their effects in real solutions are discussed. distributions and the structural and thcrtnodynamic excess quantities. Ion association (ref. I), 'coulombic unmixing' (ref. 2) and 'hydrophobic unmixing' (ref. 3) are interpreted in the framework of such interionic theorics in tcrtns of effective interactions at infinite dilution. It is advantageous for the understanding of the short-range effects usually described by 'overlapping of Gurney co- spheres' to investigate the leadin potential terms at the BO-level where both the solvent molecules and the ions are structured interacting particles of the electrolyte solution; for the volume and surface properties see (refs. 4-8). The model calculations as well as the experiments (ref. 9) at BO-level reflect a variety of features affecting the niolcc- ular pair distribution functions. The results from BO calculations and those of the solvent averaging description at thc McMillan-Mayer level may be compared with the help of integral equation techniques based on the Ornstein-Zernike equation and a Reference Hypernetted Chain (RIINC) closure relation. The underlying theory and the numerical pro- cedures are given in (refs. 7,lO-12). In the present study the defining equations for the mean force potentials at BO- and MM-level are discussed. It is shown how the Gurney term of the ion-ion interactions reproduces the properties of the solvent structure at the MM-levcl antl how tlie solvent structure influences the Coulomb interaction via tlie solvent permittivity c. In a first ste I thc contribution of solvent averaged short-range non electrostatic interactions (we call them reference system (nS\ interactions) to the solvation forces is studied with the help of hard and soft spheres and Lennard-Jones particles. In a second step we introduce electrost,atic interactions between the ions and the solvent molecules considered as polar hard spheres and Stockmayer particles. |
| Databáze: | OpenAIRE |
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