Martínez-Ruiz F J, Blas F J
Laboratorio de Simulación Molecular y Química Computacional, CIQSO-Centro de Investigación en Química Sostenible and Departamento de Física Aplicada, Universidad de Huelva, 21007 Huelva, Spain.
J Chem Phys. 2016 Apr 21;144(15):154705. doi: 10.1063/1.4947017.
We determine the interfacial properties of mixtures of spherical square-well molecules from direct simulation of the vapor-liquid interface. We consider mixtures with the same molecular size and intermolecular potential range but different dispersive energy parameter values. We perform Monte Carlo simulations in the canonical ensemble to obtain the interfacial properties of mixtures of square-well molecules. In particular, we determine the pressuretensor using the mechanical (virial) route and the vapor-liquid interfacial tension evaluated using the Irving-Kirkwood method. In addition to the pressuretensor and the surface tension, we also obtain density profiles, coexistence densities, and interfacial thickness as functions of pressure, at a given temperature. This work can be considered as the extension of our previous work [F. J. Martínez-Ruiz and F. J. Blas, Mol. Phys. 113, 1217 (2015)] to deal with mixtures of spherical molecules that interact through a discontinuous intermolecular potential. According to our results, the main effect of increasing the ratio between the dispersive energy parameters of the mixture, ϵ22/ϵ11, is to sharpen the vapor-liquid interface and to increase the width of the biphasic coexistence region. Particularly interesting is the presence of a relative maximum in the density profiles of the more volatile component at the interface. This maximum is related with adsorption or accumulation of these molecules at the interface, since there are stronger attractive interactions between these molecules in comparison with the rest of intermolecular interactions. Also, the interfacial thickness decreases and the surface tension increases as ϵ22/ϵ11 is larger, a direct consequence of the increasing of the cohesive energy of the system.
我们通过对气液界面的直接模拟来确定球形方阱分子混合物的界面性质。我们考虑分子大小相同、分子间势能范围相同但色散能量参数值不同的混合物。我们在正则系综中进行蒙特卡罗模拟，以获得方阱分子混合物的界面性质。特别地，我们使用力学（维里）方法确定压力张量，并使用欧文 - 柯克伍德方法评估气液界面张力。除了压力张量和表面张力外，在给定温度下，我们还获得了作为压力函数的密度分布、共存密度和界面厚度。这项工作可被视为我们先前工作[F. J. Martínez-Ruiz和F. J. Blas，《分子物理学》113，1217（2015）]的扩展，以处理通过不连续分子间势相互作用的球形分子混合物。根据我们的结果，增加混合物的色散能量参数之比ϵ22/ϵ11的主要影响是使气液界面变尖锐，并增加双相共存区域的宽度。特别有趣的是，在界面处挥发性较强的组分的密度分布中存在一个相对最大值。这个最大值与这些分子在界面处的吸附或积累有关，因为与其他分子间相互作用相比，这些分子之间存在更强的吸引相互作用。此外，随着ϵ22/ϵ11增大，界面厚度减小，表面张力增大，这是系统内聚能增加的直接结果。
