Department of Chemistry, New York University, New York, New York 10003, United States.
Department of Chemistry & Molecular Simulation of NonEquilibrium Processes (MSNEP), University of North Dakota, Suite 2300, Tech Accelerator, Grand Forks, North Dakota 58202, United States.
J Phys Chem B. 2020 Dec 17;124(50):11463-11471. doi: 10.1021/acs.jpcb.0c08014. Epub 2020 Dec 2.
Using flat-histogram simulations, we calculate the entropy of molecular fluids along the vapor-liquid phase boundary. Our simulation approach is based on the evaluation of the canonical and grand-canonical partition functions, which, in turn, provide access to entropy through the statistical mechanics formalism. The results allow us to determine the critical entropy of molecular fluids and to uncover that the transition occurs symmetrically from an entropic standpoint. This can best be seen through the patterns exhibited by the thermodynamic variables temperature and pressure when plotted against the entropy of the coexisting phases. This behavior is found to hold for apolar, quadrupolar, and dipolar fluids. Finally, we identify functional forms that characterize the relation between thermodynamic variables and entropy along the coexistence curve up to the critical point.
我们使用平坦直方图模拟来计算分子流体沿汽液相边界的熵。我们的模拟方法基于对正则和巨正则配分函数的评估，这些配分函数反过来通过统计力学形式主义提供了熵的途径。结果使我们能够确定分子流体的临界熵，并揭示从熵的角度来看，相变是对称发生的。这可以通过当绘制共存相的温度和压力等热力学变量与熵的关系时所显示的模式来最好地看出。这种行为适用于非极性、四极和偶极流体。最后，我们确定了特征函数形式，这些形式描述了共存曲线直至临界点的热力学变量与熵之间的关系。
