F. Otto et Gn. Patey, Forces between like-charged walls in electrolyte solution: Molecular solvent effects at the McMillan-Mayer level, J CHEM PHYS, 112(20), 2000, pp. 8939-8949
The force between two like-charged walls immersed in electrolyte solution i
s obtained for models that include solvent effects at the McMillan-Mayer (M
M) level. In these models the solvent is not represented by discrete partic
les but exerts its influence through solvent-averaged ion-ion potentials of
mean force which serve as effective potentials. This simplification allows
the numerical solution of accurate anisotropic integral equation theories,
and the anisotropic hypernetted-chain (AHNC) approximation is used in the
present calculations. It is shown that the MM results may differ significan
tly from those of the primitive model (PM) which treats the solvent as a di
electric continuum. Most interestingly, we find that at the MM level the fo
rce between like-charged walls at small separations and with realistic surf
ace charges can be attractive for monovalent counterions. This attraction i
s due to solvent effects on the effective counterion-counterion interaction
and not to the correlated charge fluctuations that give rise to the attrac
tions found for divalent counterions in the PM case. The possible relevance
of our observations in the interpretation of experimental force measuremen
ts is briefly discussed. (C) 2000 American Institute of Physics. [S0021-960
6(00)51720-6].