Electrophoretic properties of highly charged colloids: a hybrid molecular dynamics/lattice Boltzmann simulation study.
Electrophoretic properties of highly charged colloids: a hybrid molecular dynamics/lattice Boltzmann simulation study.
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高电荷胶体的电泳特性：混合分子动力学/晶格玻尔兹曼模拟研究。
DOI：
10.1063/1.2431174
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发表时间：
2006
期刊：
影响因子：
--
通讯作者：
J. Horbach
中科院分区：
文献类型：
--
作者：
A. Chatterji;J. Horbach
使用计算机模拟，在原始模型的框架内研究电解质溶液中带正电的胶体（大离子）的电泳运动。在此模型中，电解质被视为浸入无结构介质中的带负电和带正电的微离子（分别为反离子和反离子）的系统。通过应用混合模拟方案充分考虑了流体动力学相互作用，其中通过分子动力学传播的带电离子（即大离子和电解质）与晶格玻尔兹曼（LB）流体耦合。在 Martin-Molina 等人最近的一项电泳实验中。 [J。物理。化学。 B 106, 6881 (2002)]表明，对于多价盐离子，迁移率mu首先随着电荷密度σ的增加而增加，达到最大值，然后随着sigma的进一步增加而减小。目前工作的目的是阐明 mu 在高 sigma 值下的行为。即使对于单价微离子的情况，也发现 mu 随 sigma 减小。动态 Stern 层被定义为包括在受到外部电场作用时与宏离子一起移动的所有反离子。 Stern 层中反离子的数量 q(0) 是 mu 在高 sigma 值下行为的关键参数。在这种情况下，迁移率 mu 主要取决于比率 q(0)/Q（其中 Q 是大离子的化合价）。先前的论点是，随着 sigma 的增加，双电层 (EDL) 的畸变会增加，从而导致 mu 降低，但对于高 sigma 来说，这一论点并不成立。事实上，结果表明 EDL 的变形随着 sigma 的增加而减小。流体动力学相互作用的作用是通过与 Langevin 模拟的直接比较来推断的，其中与 LB 流体的耦合被关闭。此外，还考虑了具有二价抗衡离子的系统。在这种情况下，在西格玛值较高时，会发现电荷反转现象。
Using computer simulations, the electrophoretic motion of a positively charged colloid (macroion) in an electrolyte solution is studied in the framework of the primitive model. In this model, the electrolyte is considered as a system of negatively and positively charged microions (counterions and coions, respectively) that are immersed into a structureless medium. Hydrodynamic interactions are fully taken into account by applying a hybrid simulation scheme, where the charged ions (i.e., macroion and electrolyte), propagated via molecular dynamics, are coupled to a lattice Boltzmann (LB) fluid. In a recent electrophoretic experiment by Martin-Molina et al. [J. Phys. Chem. B 106, 6881 (2002)], it was shown that, for multivalent salt ions, the mobility mu initially increases with charge density sigma, reaches a maximum, and then decreases with further increase of sigma. The aim of the present work is to elucidate the behavior of mu at high values of sigma. Even for the case of monovalent microions, a decrease of mu with sigma is found. A dynamic Stern layer is defined that includes all the counterions that move with the macroion while subjected to an external electrical field. The number of counterions in the Stern layer, q(0), is a crucial parameter for the behavior of mu at high values of sigma. In this case, the mobility mu depends primarily on the ratio q(0)/Q (with Q the valency of the macroion). The previous contention that the increase in the distortion of the electric double layer (EDL) with increasing sigma leads to the lowering of mu does not hold for high sigma. In fact, it is shown that the deformation of the EDL decreases with the increase of sigma. The role of hydrodynamic interactions is inferred from direct comparisons to Langevin simulations where the coupling to the LB fluid is switched off. Moreover, systems with divalent counterions are considered. In this case, at high values of sigma the phenomenon of charge inversion is found.