Ion Pair PotentialsofMeanForce in Water
Abstract
Recent molecular simulation and integral equation results alkalihalide ion pair potentialsofmeanforce in water are discussed. Dielectric model calculations are implemented to check that these models produce that characteristic structure of contact and solventseparated minima for oppositely charged ions in water under physiological thermodynamic conditions. Comparison of the dielectric model results with the most current molecular level information indicates that the dielectric model does not, however, provide an accurate description of these potentialsofmeanforce. We note that linear dielectric models correspond to modelistic implementations of secondorder thermodynamic perturbation theory for the excess chemical potential of a distinguished solute molecule. Therefore, the molecular theory corresponding to the dielectric models is secondorder thermodynamic perturbation theory for that excess chemical potential. The secondorder, or fluctuation, term raises a technical computational issue of treatment of longranged interactions similar to the one which arises in calculation of the dielectric constant of the solvent. It is contended that the most important step for further development of dielectric models would be a separate assessment of the firstorder perturbative term (equivalently the {\it potential at zero charge} ) which vanishes in the dielectric models but is generally nonzero. Parameterization of radii and molecular volumes should then be based of the secondorder perturbative term alone. Illustrative initial calculations are presented and discussed.
 Publication:

arXiv eprints
 Pub Date:
 April 1994
 arXiv:
 arXiv:chemph/9404001
 Bibcode:
 1994chem.ph...4001P
 Keywords:

 Physics  Chemical Physics
 EPrint:
 37 pages and 8 figures. LAUR934205