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arXiv 1206.5686cond-mat.soft
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环路膨胀后非均匀带电流体中的静电关联

Electrostatic correlations in inhomogeneous charged fluids beyond loop expansion

Sahin Buyukdagli, Cristian Achim, Tapio Ala-Nissila

摘要:

本文用静电自洽理论研究了非均匀对称电解质中的静电关联效应。Netz和H.奥兰J. E 11,301(2003))。为了这个目的,我们介绍了两种计算方法,允许解决SC方程以外的循环扩展。这两种方法都可以处理的情况下,介电不连续的边界的单回路理论是已知的失败。通过将从这些方案获得的理论结果与我们在中性单电介质界面处运行的离子的MC模拟结果以及先前的带电界面的MC数据进行比较,我们首先表明弱耦合(WC)Debye-Huckel(DH)理论在体离子密度rhob=0.01 M之前仍然定量准确,而SC理论在rhob= 0.2M时表现出良好的定量精度。然后,我们从微扰SC格式导出了介电均匀带电表面周围非对称分区盐体系的单圈理论。结果表明,相关效应起源于这些系统从盐屏蔽损失之间的竞争,在界面上驱动的离子的散装区域,和界面的countershielding过剩吸引他们向表面。在弱表面电荷的情况下,界面盐屏蔽损失是主要的影响。因此,相关性降低了共离子和反离子的MF密度。随着表面电荷的增加,表面吸引的反离子屏蔽过剩开始占主导地位,相关效应放大这两种类型的离子的MF密度。我们还表明,在一个特征值的静电耦合参数,静电相关的结果在电荷反转效应。

英文摘要:

Electrostatic correlation effects in inhomogeneous symmetric electrolytes are investigated within a previously developed electrostatic self-consistent (SC) theory (R.R. Netz and H. Orland, Eur. Phys.J. E 11, 301 (2003)). To this aim, we introduce two computational approaches that allow to solve the SC equations beyond the loop expansion. Both approaches can handle the case of dielectrically discontinuous boundaries where the one-loop theory is known to fail. By comparing the theoretical results obtained from these schemes with the results of the MC simulations that we ran for ions at neutral single dielectric interfaces as well as with previous MC data for charged interfaces, we first show that the weak coupling (WC) Debye-Huckel (DH) theory remains quantitatively accurate up to the bulk ion density rhob=0.01 M, whereas the SC theory exhibits a good quantitative accuracy up to rhob=0.2 M. Then, we derive from the perturbative SC scheme the one-loop theory of asymmetrically partitioned salt systems around a dielectrically homogeneous charged surface. It is shown that correlation effects originate in these systems from a competition between the salt screening loss at the interface driving the ions to the bulk region, and the interfacial counterion screening excess attracting them towards the surface. In the case of weak surface charges, the interfacial salt screening loss is the dominant effect. As a result, correlations decrease the MF density of both coions and counterions. With increasing surface charge, the surface-attractive counterion screening excess starts to dominate, and correlation effects amplify in this regime the MF density of both type of ions. We also show that at a characteristic value of the electrostatic coupling parameter, electrostatic correlations result in a charge inversion effect.

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