Department of Chemical Engineering, Brigham Young University, Provo, Utah 84602, USA.
J Chem Phys. 2011 Jan 14;134(2):024101. doi: 10.1063/1.3528117.
Molecular dynamics simulations were performed to determine two-phase configurations of model propane molecules below the critical point and in the near-critical, two-phase region. A postprocessor that uses a Monte Carlo method for determination of volumes attributable to each molecule was used to obtain density histograms of the particles from which the bulk coexisting equilibrium vapor and liquid densities were determined. This method of analyzing coexisting densities in a two-phase simulation is straightforward and can be easily implemented for complex, multisite models. Various degrees of internal flexibility in the propane models have little effect on the coexisting densities at temperatures 40 K or more below the critical point, but internal flexibility (angle bending and bond vibrations) does affect the saturated liquid densities in the near-critical region, changing the critical temperature by approximately 20 K. Shorter cutoffs were also found to affect the phase dome and the location of the critical point.
采用分子动力学模拟方法，研究了临界点以下及近临界区模型丙烷分子的二相结构。我们使用了一个后处理器，该处理器采用蒙特卡罗方法来确定每个分子的体积，从而获得颗粒的密度直方图，由此确定共存平衡蒸汽和液体的密度。这种在二相模拟中分析共存密度的方法简单直接，可方便地应用于复杂的多站点模型。在温度比临界点低 40 K 或更多的情况下，丙烷模型的不同程度的内部灵活性对共存密度几乎没有影响，但内部灵活性（角度弯曲和键振动）确实会影响近临界区的饱和液体密度，使临界温度变化约 20 K。还发现较短的截止值会影响相区和临界点的位置。
