Department of Chemical and Biological Engineering, University at Buffalo, The State University of New York, Buffalo, New York 14260-4200, USA.
J Chem Phys. 2013 Aug 14;139(6):064110. doi: 10.1063/1.4817535.
We introduce Monte Carlo simulation methods for determining interfacial properties of fluids that exhibit bulk liquid-liquid immiscibility. An interface-potential-based approach, in which the interfacial properties of a system are related to the surface excess free energy of a thin fluid film in contact with a surface, is utilized to deduce the wetting characteristics of these systems. We present a framework for implementing this general method within both the grand canonical and semigrand isobaric-isothermal ensembles. Tracking the evolution of interfacial properties along various thermodynamic paths is also examined. This task is accomplished by implementing variants of the expanded ensemble technique, which enables one to obtain components of the interface potential along a path of interest. We also discuss how these concepts are employed to calculate bulk liquid-liquid coexistence properties in an efficient manner. The computational strategies introduced here are applied to three model Lennard-Jones systems. For each system, we compile the evolution of the liquid-liquid surface tension and contact angle with temperature or pressure. For one of the model systems we compare our results with literature data. We also examine how interfacial properties evolve upon variation of the relative affinity of the fluid components for the substrate. Overall, we find that the approach pursued here is generally applicable and provides an efficient and precise means to calculate the bulk and interfacial properties of fluids that exhibit liquid-liquid immiscibility.
我们介绍了用于确定表现出体相液-液相不混溶性的流体界面性质的蒙特卡罗模拟方法。我们利用基于界面势的方法，其中系统的界面性质与与表面接触的薄流体膜的表面过剩自由能相关联，来推断这些系统的润湿特性。我们提出了在巨正则和半巨正则等压-等温系综中实现这种通用方法的框架。还研究了沿着各种热力学路径跟踪界面性质的演变。通过实现扩展系综技术的变体来完成此任务，这使得人们能够沿着感兴趣的路径获得界面势的分量。我们还讨论了如何以有效的方式利用这些概念来计算体相液-液相共存性质。这里介绍的计算策略应用于三个模型 Lennard-Jones 系统。对于每个系统，我们编译了液体-液体表面张力和接触角随温度或压力的演化。对于其中一个模型系统，我们将我们的结果与文献数据进行了比较。我们还研究了在流体组分对基底的相对亲和力变化时界面性质如何演变。总体而言，我们发现这里采用的方法具有普遍适用性，并且提供了一种有效且精确的方法来计算表现出液-液相不混溶性的流体的体相和界面性质。
