Granados-Bazán Eder L, Quiñones-Cisneros Sergio E, Deiters Ulrich K
Institute of Physical Chemistry, University of Cologne, Luxemburger Str. 116, 50939 Köln, Germany.
Institute of Thermo- and Fluid Dynamics, Ruhr-University Bochum, Universitätsstr. 150, 44801 Bochum, Germany.
J Chem Phys. 2021 Feb 28;154(8):084704. doi: 10.1063/5.0042340.
Binary mixtures of fully flexible linear tangent chains composed of bonded Lennard-Jones interaction sites (monomers) were studied using the molecular dynamics simulation in the NVT ensemble. Their interfacial properties were investigated in planar interfaces by direct simulation of an explicit liquid film in equilibrium with its vapor. A method for the calculation of long-range interactions in inhomogeneous fluids was implemented to take into account the potential truncation effects. Surface tension and the pressure tensor were calculated via the classical Irving-Kirkwood method; vapor pressure, orthobaric densities, density profiles, and Gibbs relative adsorption of the volatile component with respect to the heavy component were also obtained. The properties were studied as a function of the temperature, molar concentration of the heavy component, and the asymmetry of the mixture. According to the results of this work, the temperature loses influence on the surface tension, vapor pressure, and Gibbs relative adsorption curves as the molecular length of the heavy component increases. This suggests that the universal behavior observed in pure fluids of Lennard-Jones chains also holds for binary mixtures. The contribution of the long-range interactions turned out to account for about 60%, 20%, and 10% of the surface tension, vapor pressure, and orthobaric density final values, respectively. This contribution was even larger at high temperatures and for large molecules. Strong enrichment of the volatile component at the interface was observed in the asymmetric mixtures. One of these mixtures even showed a barotropic effect at elevated pressures and a class III phase behavior.
使用NVT系综中的分子动力学模拟研究了由键合的 Lennard-Jones 相互作用位点（单体）组成的完全柔性线性切线链的二元混合物。通过直接模拟与气相处于平衡状态的显式液膜，在平面界面中研究了它们的界面性质。实施了一种计算非均匀流体中长程相互作用的方法，以考虑势截断效应。通过经典的欧文-柯克伍德方法计算表面张力和压力张量；还获得了蒸气压、正压密度、密度分布以及挥发性组分相对于重组分的吉布斯相对吸附。研究了这些性质作为温度、重组分摩尔浓度和混合物不对称性的函数。根据这项工作的结果，随着重组分分子长度的增加，温度对表面张力、蒸气压和吉布斯相对吸附曲线的影响减小。这表明在 Lennard-Jones 链的纯流体中观察到的普遍行为也适用于二元混合物。结果表明，长程相互作用的贡献分别约占表面张力、蒸气压和正压密度最终值的60%、20%和10%。在高温和大分子情况下，这种贡献甚至更大。在不对称混合物中观察到挥发性组分在界面处强烈富集。其中一种混合物在高压下甚至表现出正压效应和III类相行为。
