Classical density functional theory and Monte Carlo simulation study of electric double layer in the vicinity of a cylindrical electrode
Classical density functional theory and Monte Carlo simulation study of electric double layer in the vicinity of a cylindrical electrode
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DOI：
10.1088/1742-5468/aa79af
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发表时间：
2017-07
期刊：
影响因子：
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通讯作者：
Shiqi Zhou;S. Lamperski;M. Sokołowska
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文献类型：
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作者：
Shiqi Zhou;S. Lamperski;M. Sokołowska
我们已经进行了广泛的蒙特-卡罗模拟和经典的密度泛函理论（DFT）计算的双电层（EDL）附近的圆柱形电极在一个原始模型（PM）修改，纳入电子色散相互作用。得出的结论是：（i）一般来说，简单地使用平均场（MF）近似计算电子色散相互作用不会明显恶化经典DFT的性能，即使考虑的盐离子在尺寸（3：1）和电荷（5：1）上高度不对称，考虑的体摩尔浓度高达0.314的总体离子堆积分数，表面电荷密度高达0.5 C m−2。(ii)更具体地说，考虑到可能的噪声在模拟中，局部体电荷密度分布是最准确地预测的经典DFT在所有情况下，和合作和反离子单重态分布也相当准确地预测，而平均静电势分布是相对不太准确的预测，由于一个积分放大的单重态分布的微小不准确性。(iii)发现只有当表面电荷密度足够高（例如0.5 C m−2）时，共离子分布的层状结构才是异常可能的;此外，共离子价态异常影响第一反离子层的峰高，第一反离子层的峰高随着共离子价态的降低而降低。(iv)即使模拟和DFT都表明电子色散相互作用对上述三个“局部”量的贡献微不足道，但经典DFT清楚地表明，电子色散相互作用确实显著影响“全局”量，如圆柱表面-电解质水溶液界面张力，这可能意味着电子色散相互作用在解释特定的Hofmeister效应中的作用。我们阐明了所有上述观察的基础上的论点，从液态理论和分子尺度。
We have performed extensive Monte-Carlo simulations and classical density functional theory (DFT) calculations of the electrical double layer (EDL) near a cylindrical electrode in a primitive model (PM) modified by incorporating interionic dispersion interactions. It is concluded that (i) in general, an unsophisticated use of the mean field (MF) approximation for the interionic dispersion interactions does not distinctly worsen the classical DFT performance, even if the salt ions considered are highly asymmetrical in size (3:1) and charge (5:1), the bulk molar concentration considered is high up to a total bulk ion packing fraction of 0.314, and the surface charge density of up to 0.5 C m−2. (ii) More specifically, considering the possible noises in the simulation, the local volume charge density profiles are the most accurately predicted by the classical DFT in all situations, and the co- and counter-ion singlet distributions are also rather accurately predicted; whereas the mean electrostatic potential profile is relatively less accurately predicted due to an integral amplification of minor inaccuracy of the singlet distributions. (iii) It is found that the layered structure of the co-ion distribution is abnormally possible only if the surface charge density is high enough (for example 0.5 C m−2); moreover, the co-ion valence abnormally influences the peak height of the first counter-ion layer, which decreases with the former. (iv) Even if both the simulation and DFT indicate an insignificant contribution of the interionic dispersion interaction to the above three ‘local’ quantities, it is clearly shown by the classical DFT that the interionic dispersion interaction does significantly influence a ‘global’ quantity like the cylinder surface-aqueous electrolyte interfacial tension, and this may imply the role of the interionic dispersion interaction in explaining the specific Hofmeister effects. We elucidate all of the above observations based on the arguments from the liquid state theory and at the molecular scale.