Gaussian Charge Distributions for Incorporation of Electrostatic Interactions in Dissipative Particle Dynamics: Application to Self-Assembly of Surfactants
Gaussian Charge Distributions for Incorporation of Electrostatic Interactions in Dissipative Particle Dynamics: Application to Self-Assembly of Surfactants
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DOI：
10.1021/acs.jctc.9b00174
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发表时间：
2019-07-01
影响因子：
5.5
通讯作者：
Mueller-Plathe, Florian
中科院分区：
文献类型：
--
作者：
Eslami, Hossein;Khani, Marzieh;Mueller-Plathe, Florian
点电荷通过宽度可调的高斯分布在软耗散粒子动力学(DPD)微珠上。用更宽的相反电荷的高斯分布来屏蔽高斯涂抹的电荷分布，将静电相互作用分裂为实空间贡献和倒易空间贡献。该方法在文献中的模型试验系统上得到了验证。该方法还被用来研究十二烷基硫酸钠(SDS)在水中的自组装。在十二烷基硫酸钠浓度从临界胶束浓度变化到比临界胶束浓度大20倍的溶液中，自由表面活性剂的临界胶束浓度(CMC)和平衡浓度与实验结果基本一致。胶束的微观结构及其疏水/亲水基团和反离子在水界面的分布与实验相符。根据胶束尺寸随时间波动的间歇和连续关联函数，考察了胶束与溶液之间单体交换的动力学。发现了两个松弛时间相差2个数量级的离散松弛过程。使用根据热速度定义的自然DPD时间单位，松弛时间比实验松弛时间短一个数量级，用于单体交换和通过表面活性剂的扩散在溶液和胶束之间建立平衡的实验松弛时间。然而，通过定义DPD时间尺度以使计算的水的扩散系数与其实验值相对应，可以获得实验上可比较的驰豫时间。
The point charges are distributed over the soft dissipative particle dynamics (DPD) beads using a Gaussian of tunable width. Screening the Gaussian smeared charge distributions, with wider Gaussians of opposite charge, splits the electrostatic interaction into the real- and the reciprocal-space contributions. This method is validated against model test systems in the literature. The method has also been employed to study self-assembly in solutions of sodium dodecyl sulfate (SDS) in water. The critical micelle concentration (CMC) and the equilibrium concentration of free surfactants, in solutions with SDS concentrations varying from CMC to approximate to 20 times larger than CMC, are in close agreement with experiment. The microscopic structure of the micelles and the distributions of its hydrophobic/hydrophilic groups and counterions at the water interface are in agreement with experiment. The dynamics of monomer exchange between micelles and solution is examined in terms of the intermittent and continuous correlation functions for the fluctuation of micelle size with time. Two discrete relaxation processes, whose relaxation times differ by 2 orders of magnitude are found. Using the natural DPD time unit, defined in terms of thermal velocity, the relaxation times are an order of magnitude shorter than experimental relaxation times for monomer exchange and establishment of equilibrium between surfactants in the solution and micelles through diffusion of surfactants. However, experimentally comparable relaxation times are obtained by defining the DPD time scale such that the calculated diffusion coefficient of water corresponds to its experimental value.