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arXiv 1209.2500cond-mat.mes-hallphysics.chem-phphysics.comp-ph
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纳米通道中电荷输运的分子理论

Charge transport in nanochannels: a molecular theory

Umberto Marini Bettolo Marconi, Simone Melchionna

摘要:

本文介绍了一种理论和数值方法来研究极端约束条件下带电流体混合物的流动。我们建模的电解质溶液作为一个三元混合物,包括两个相反的电荷和第三个不带电的组件的离子物种。微观方法是基于动力学理论,是完全自洽的。它允许确定配置属性,如附近的限制壁分层,和流动特性。我们表明,在适当的假设下,该方法再现用于描述电动现象的唯象方程,而不需要引入本构方程来确定通量。此外,我们模拟通道的任意形状和纳米粗糙度,这些系统的传输特性有重要影响的功能。数值模拟是通过求解每种物质的单粒子相空间分布的演化动力学,通过格子玻尔兹曼方法在直和楔形通道中的流动。结果的微观密度,速度分布和体积和电荷流量。强偏离电中性显示出现在分子水平。

英文摘要:

We introduce a theoretical and numerical method to investigate the flow of charged fluid mixtures under extreme confinement. We model the electrolyte solution as a ternary mixture, comprising two ionic species of opposite charge and a third uncharged component. The microscopic approach is based on kinetic theory and is fully self-consistent. It allows to determine configurational prop- erties, such as layering near the confining walls, and the flow properties. We show that, under appropriate assumptions, the approach reproduces the phenomenological equations used to describe electrokinetic phenomena, without requiring the introduction of constitutive equations to determine the fluxes. Moreover, we model channels of arbitrary shape and nanometric roughness, features that have important repercussions on the transport properties of these systems. Numerical simulations are obtained by solving the evolution dynamics of the one-particle phase- space distributions of each species by means of a Lattice Boltzmann method for flows in straight and wedged channels. Results are presented for the microscopic density, the velocity profiles and for the volumetric and charge flow-rates. Strong departures from electroneutrality are shown to appear at molecular level.

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