Department of Chemical and Biological Engineering, University at Buffalo, The State University of New York, Buffalo, New York 14260-4200, USA.
J Chem Phys. 2010 Jun 14;132(22):224702. doi: 10.1063/1.3431525.
We examine several issues related to the calculation of interfacial properties via analysis of an interface potential obtained from grand canonical Monte Carlo simulation. Two model systems are examined. One includes a monatomic Lennard-Jones fluid that interacts with a structureless substrate via a long-ranged substrate potential. The second model contains a monatomic Lennard-Jones fluid that interacts with an atomistically detailed substrate via a short-ranged potential. Our results are presented within the context of locating the wetting point. Two methods are used to compute the wetting temperature. In both cases we examine the system size dependence of the key property used to deduce the wetting temperature as well as the robustness of the scaling relationship employed to describe the evolution of this property with temperature near the wetting point. In the first approach we identify the wetting transition as the point at which the prewetting and bulk saturation curves meet. In this case, the prewetting saturation chemical potential is the key quantity of interest. In the second approach we find the point at which the spreading coefficient evaluates to zero. We find that the effect of system size is adequately described by simple scaling functions. Moreover, estimates of the wetting temperature for finite-sized systems characterized by a linear dimension greater than 12 fluid diameters differ by less than 1% from an otherwise equivalent macroscopic system. Modification of the details regarding the use of simulation data to compute the wetting temperature can also produce a shift in this quantity of up to 1%. As part of this study, we also examine techniques for describing the shape of the interface potential at a relatively high surface density. This analysis is particularly relevant for systems with long-ranged substrate potentials for which the interface potential approaches a limiting value asymptotically.
我们通过分析由巨正则蒙特卡罗模拟获得的界面势来研究与界面性质计算相关的几个问题。我们检验了两个模型体系。其中一个体系包括一个单原子 Lennard-Jones 流体，该流体通过长程的基底势与无定形的基底相互作用。第二个模型包含一个单原子 Lennard-Jones 流体，该流体通过短程势与原子级细节的基底相互作用。我们的结果是在确定润湿点的背景下给出的。我们使用两种方法来计算润湿温度。在这两种情况下，我们都研究了用于推断润湿温度的关键性质的系统尺寸依赖性，以及用于描述该性质随接近润湿点的温度变化的标度关系的稳健性。在第一种方法中，我们将润湿转变定义为预润湿和体相饱和度曲线相交的点。在这种情况下，预润湿饱和化学势是感兴趣的关键量。在第二种方法中，我们找到使扩展系数评估为零的点。我们发现，系统尺寸的影响可以通过简单的标度函数来充分描述。此外，用线性尺寸大于 12 个流体直径的有限尺寸系统来表示的润湿温度的估计值与具有相同尺寸的宏观系统相比，仅相差不到 1%。通过修改有关使用模拟数据计算润湿温度的细节，也可以使这个量发生高达 1%的变化。作为这项研究的一部分，我们还研究了在相对高的表面密度下描述界面势形状的技术。对于具有长程基底势的体系，该分析特别重要，因为界面势在渐近线处趋于一个极限值。
