Department of Physics and Astronomy and Ames Laboratory, Iowa State University, Ames, Iowa 50010, USA.
J Chem Phys. 2012 Aug 14;137(6):064708. doi: 10.1063/1.4739300.
We provide extensive molecular dynamics simulations of counterion and coion distributions near an impenetrable plane with fixed discrete charges. The numerical results are described by an explicit solution that distinguishes the plasma (√(A(c))/σ>3) and the binding regime (√(A(c))/σ<3) where σ is the ion diameter and A(c) = ∣e∕ν∣ (ν is the surface charge density). In the plasma regime, the solution consists of a product of two functions that can be computed from simpler models and reveals that the effects of the discreteness of the charge extends over large distances from the plane. The solution in the binding regime consists of a Stern layer of width σ and a diffuse layer, but contrary to standard approaches, the strong correlations between ions within the Stern layer and the diffuse layer require a description in terms of a "displaced" diffuse layer. The solution is found to describe electrolytes of any valence at all concentrations investigated (up to 0.4M) and includes the case of additional specific interactions such as van der Waals attraction and other generalizations. We discuss some open questions.
我们提供了广泛的离子和反离子在固定离散电荷的不可穿透平面附近分布的分子动力学模拟。数值结果由一个显式解描述，该解区分了等离子体（√（A（c））/σ>3）和结合区域（√（A（c））/σ<3），其中σ是离子直径，A（c）=∣e∕ν∣（ν是表面电荷密度）。在等离子体区域，该解由两个可以从更简单的模型计算的函数的乘积组成，并揭示了电荷离散性的影响在远离平面的很大距离上延伸。在结合区域的解由宽度为σ的斯特恩层和扩散层组成，但与标准方法相反，斯特恩层和扩散层内离子之间的强相关性需要用“位移”扩散层来描述。该解被发现可以描述在所研究的所有浓度（高达 0.4M）的任何价电解质，并且包括范德华吸引力和其他概括等附加特定相互作用的情况。我们讨论了一些悬而未决的问题。
