Molecular Dynamics Exploration of the Effects of Dissolved Ionic Additives on Interfacial Region Structure and Heat and Mass Transfer in Thin Liquid Films

溶解离子添加剂对液膜界面区结构和传热传质影响的分子动力学研究货车P. Carey加州大学伯克利分校机械工程系，CA（NSF提案0456982）项目摘要拟议的研究将包括两种不同类型的分子动力学（MD）的发展模拟，将用于探索溶解的离子物种的界面区域的结构和传热传质薄液态水膜的影响。 我们将使用两种不同类型的模拟来探索离子添加剂在两种情况下的影响：（1）在体相之间的自由薄液膜中，以及（2）在固体表面上的薄液膜中。 建议的MD模拟将探讨如何影响的离子的界面区域结构，界面张力，和水膜的稳定性。 他们还将探索先前观察到的薄膜中定向质量扩散系数和定向热导率的变化。 在这些模拟中，每个物种的适当的势函数将被用来模拟水分子，离子和壁原子之间的力的相互作用。 MD模拟将使用纯水和水和NaCl的稀溶液以及水和KCl在溶质摩尔分数、膜厚度和系统压力的宽范围条件下运行。 溶液模拟结果将被广泛分析，以确定离子浓度的变化如何影响界面区域结构，近界面性能，和膜的稳定性。 这项研究将推进最先进的MD模拟方法，它将提供一个分子水平的理解离子如何影响气泡合并过程和近界面的运输和稳定性的液态水膜固体表面。 由于这些现象在许多常见的沸腾和冷凝过程中起着核心作用，这些研究的结果将有助于铸造金属零件的水淬火，微蒸发器设计以及薄膜蒸发或冷凝重要的许多其他应用的技术进步。 在界面区域的运输的探索将澄清所观察到的各向异性的质量扩散和传热的机制。 在界面区域中的运输的这一特征可能是至关重要的表面活性剂在界面上的传播过程中的瞬态过程中，并在分子组装方案，其中建设发生在液体-蒸汽界面。 离子对水界面现象的影响也将有助于了解在液态水界面的生物和环境过程。 本研究的本科研究部分旨在鼓励代表性不足的本科生考虑MD模拟方法，高级计算或纳米工程的研究生课程。

Molecular Dynamics Exploration of the Effects of Dissolved Ionic Additives on Interfacial Region Structure and Heat and Mass Transfer in Thin Liquid Films Van P. CareyMechanical Engineering DepartmentUniversity of California, Berkeley, CA(NSF proposal 0456982)Project Abstract The proposed research will include development of two different types of molecular dynamics (MD) simulations that will be used to explore the effects of dissolved ionic species on the interfacial region structure and heat and mass transfer in thin liquid water films. We will use the two different types of simulations to explore the effects of ionic additives in two contexts: (1) in a free thin liquid film between bulk phases, and (2) in a thin liquid film on a solid surface. The proposed MD simulations will explore how the ions affect the interfacial region structure, the interfacial tension, and the stability of water films. They will also explore the previously observed variation of the directional mass diffusion coefficients and the directional thermal conductivities in the film. In these simulations, appropriate potential functions for each species will be used to model force interactions among water molecules, ions and wall atoms. MD simulations will be run with pure water and dilute solutions of water and NaCl, and water and KCl for conditions spanning wide ranges of solute mole fraction, film thickness and system pressure. The solution simulation results will be extensively analyzed to determine how variation of ion concentration affects interfacial region structure, near interface properties, and film stability. This research will advance the state of the art for MD simulation methods and it will provide a molecular level understanding of how ions affect bubble merging processes and near-interface transport and stability in liquid water films on solid surfaces. Because these phenomena play central roles in many common boiling and condensation processes, the results of these studies will contribute to technological advancements in water quenching of cast metal parts, microevaporator design, and a number of other applications in which thin film evaporation or condensation is important. The exploration of transport in the interfacial region will clarify the mechanism of the observed anisotropic mass diffusion and heat transfer. This feature of transport in the interfacial region may be critically important in the spread of surfactants over the interface during transient processes, and in molecular assembly schemes in which construction occurs at a liquid-vapor interface. The effects of ions on interfacial phenomena in water revealed by this investigation will also contribute to the understanding of biological and environmental processes at a liquid water interface. An undergraduate research component of this research will aim to encourage underrepresented undergraduate students to consider graduate studies in MD simulation methods, advanced computing or nanoengineering.