Fraction of condensed counterions around a charged rod: Comparison of Poisson-Boltzmann theory and computer simulations
Fraction of condensed counterions around a charged rod: Comparison of Poisson-Boltzmann theory and computer simulations
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DOI：
10.1021/ma990897o
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发表时间：
2000-01-11
期刊：
影响因子：
5.5
通讯作者：
May, S
中科院分区：
文献类型：
--
作者：
Deserno, M;Holm, C;May, S
本文研究了高电荷刚性聚电解质溶液中的反凝聚现象。提出了一种基于电荷分布函数的方法来确定凝聚离子的分数和凝聚层的径向延伸。在无盐泊松-玻尔兹曼（PB）理论中，它再现了众所周知的分数1-1/xi。的凝聚离子的曼宁参数xi > 1。此外，它预测了弱盐依赖性的这部分和崩溃的概念，在高盐限制的反凝聚。我们补充我们的理论研究与分子动力学模拟的细胞状模型，不断产生更强的凝聚比PB理论预测。虽然理论和模拟之间的协议是优秀的单价，弱电荷的情况下，它恶化的静电相互作用强度的增加，特别是，增加价。例如，在高浓度的二价盐和大的xi，我们的计算机模拟预测的电荷振荡，平均场理论无法重现。
We investigate the phenomenon of counterion condensation in a solution of highly charged rigid polyelectrolytes within the cell model. A method is proposed which-based on the charge distribution function-identifies both the fraction of condensed ions and the radial extension of the condensed layer. Within salt-free Poisson-Boltzmann (PB) theory it reproduces the well-known fraction 1-1/xi. of condensed ions for a Manning parameter xi > 1. Furthermore, it predicts a weak salt dependence of this fraction and a breakdown of the concept of counterion condensation in the high-salt limit. We complement our theoretical investigations with molecular dynamics simulations of a cell-like model, which constantly yield a stronger condensation than predicted by PB theory. While the agreement between theory and simulation is excellent in the monovalent, weakly charged case, it deteriorates with increasing electrostatic interaction strength and, in particular, increasing valence. For instance, at a high concentration of divalent salt and large xi our computer simulations predict charge oscillations, which mean-field theory is unable to reproduce.