Theoretical Chemistry Section, Chemistry Group, Bhabha Atomic Research Centre, Mumbai 400 085, India.
J Phys Chem B. 2010 Aug 19;114(32):10550-7. doi: 10.1021/jp1042975.
The structure of spherical electric double layers in the presence of mixed electrolytes is studied using Monte Carlo simulation and density functional theory within the restricted primitive model. The macroion is modeled as an impenetrable charged hard sphere carrying a uniform surface charge density, surrounded by the small ions represented as charged hard spheres, and the solvent is taken as a dielectric continuum. The density functional theory uses a partially perturbative scheme, where the hard-sphere contribution to the one-particle correlation function is evaluated using weighted density approximation and the ionic interactions are calculated using a second-order functional Taylor expansion with respect to a bulk electrolyte. The Monte Carlo simulations have been performed in canonical ensemble. The system is studied at varying ionic concentrations, at different concentration ratios of mono- and multivalent counterions of mixed electrolytes, at different diameters of hard spheres, at different macroion radius, and at varying polyion surface charge densities. The theoretical predictions in terms of the density profiles and the mean electrostatic potential profiles are found to be in good agreement with the simulation results. This model study shows clear manipulations of ionic size and charge correlations in dictating a number of interesting phenomena relating to width of the diffuse layer and charge inversion under different parametric conditions.
采用蒙特卡罗模拟和密度泛函理论，在受限原始模型内研究了混合电解质存在下的球形电双层结构。宏观离子被建模为带均匀表面电荷密度的不可穿透带电硬球，周围是带电硬球表示的小离子，而溶剂被视为介电连续体。密度泛函理论使用部分微扰方案，其中使用加权密度近似法评估硬球对单粒子相关函数的贡献，并且使用相对于本体电解质的二阶泛函泰勒展开计算离子相互作用。蒙特卡罗模拟在正则系综中进行。在不同的离子浓度、混合电解质的单价和多价抗衡离子的不同浓度比、不同的硬球直径、不同的宏观离子半径以及不同的多离子表面电荷密度下研究了该系统。发现密度分布和平均静电势分布的理论预测与模拟结果非常吻合。该模型研究清楚地说明了离子大小和电荷相关性的操纵，在不同参数条件下，在影响与扩散层宽度和电荷反转有关的许多有趣现象方面具有重要意义。
