Fawcett W Ronald, Henderson Douglas J
Department of Chemistry, University of California, Davis, California 95616, USA.
J Phys Chem B. 2005 Dec 1;109(47):22608-13. doi: 10.1021/jp0541112.
The equations needed to estimate the potential drop across the diffuse layer according to the hypernetted chain approximation (HNCA) are derived in this paper for 2:1 and 1:2 electrolytes at the restricted primitive level. It is shown that HNCA results can be expressed in the same format as the corresponding Gouy-Chapman equations with inclusion of two modifying functions. One function depends on the fraction of the solution volume occupied by the ions, and the other depends on the reciprocal thickness of the ionic atmosphere surrounding each ion. In addition, an expression for the potential profile in the diffuse layer for 2:1 and 1:2 electrolyte solutions is derived according to Gouy-Chapman theory. The modifying functions in the HNCA are then estimated using the Henderson-Blum approach for solutions containing ions with diameters of 300 and 400 pm for concentrations in the range from 0.1 to 2 M. It is shown that the Henderson-Blum approach is inadequate for systems with multivalent ions except for charge densities very close to the point of zero charge.
本文针对2:1和1:2电解质，在受限原始水平下，推导了根据超网链近似（HNCA）估算扩散层上电位降所需的方程。结果表明，HNCA结果可以用与相应的 Gouy-Chapman 方程相同的形式表示，其中包含两个修正函数。一个函数取决于离子占据的溶液体积分数，另一个函数取决于围绕每个离子的离子氛的倒数厚度。此外，根据 Gouy-Chapman 理论推导了2:1和1:2电解质溶液扩散层中电位分布的表达式。然后，使用 Henderson-Blum 方法对浓度范围为0.1至2 M、离子直径为300和400 pm的溶液估算HNCA中的修正函数。结果表明，除了电荷密度非常接近零电荷点的系统外，Henderson-Blum方法对于多价离子系统是不适用的。
