Kamath Ganesh, Georgiev Grigor, Potoff Jeffrey J
Department of Chemical Engineering and Materials Science, Wayne State University, Detroit, Michigan 48202, USA.
J Phys Chem B. 2005 Oct 20;109(41):19463-73. doi: 10.1021/jp0535238.
Force fields based on a Lennard-Jones (LJ) 12-6 plus point charge functional form are developed for acetone and chloroform specifically to reproduce the minimum pressure azeotropy found experimentally in this system. Point charges are determined from a CHELPG population analysis performed on an acetone-chloroform dimer. The required electrostatic surface for this dimer is determined from ab initio calculations performed with MP2 theory and the 6-31g++(3df,3pd) basis set. LJ parameters are then optimized such that the liquid-vapor coexistence curve, critical parameters, and vapor pressures are well reproduced by simulation. Histogram-reweighting Monte Carlo simulations in the grand canonical ensemble are used to determine the phase diagrams for the binary mixtures acetone-chloroform, acetone-methanol, and chloroform-methanol. The force fields developed in this work reproduce the minimum pressure azeotrope in the acetone-chloroform mixture found in experiment. The predicted azeotropic composition of x(CHCl3) = 0.77 is in fair agreement with the experimental value of x(CHCl3)expt = 0.64. The new force fields were also found to provide improved predictions of the pressure-composition behavior of acetone-methanol and chloroform-methanol when compared to other force fields commonly used for vapor-liquid equilibria calculations. NPT simulations were conducted at 300 K and 1 bar for equimolar mixtures of acetone-chloroform, acetone-methanol, and methanol-chloroform. Analysis of the microstructure reveals significant hydrogen bonding occurring between acetone and chloroform. Limited interspecies hydrogen bonding was found in the acetone-methanol or chloroform-methanol mixtures.
基于 Lennard-Jones（LJ）12 - 6 加点电荷函数形式开发了针对丙酮和氯仿的力场，专门用于重现该体系中实验发现的最低压力共沸物。点电荷由对丙酮 - 氯仿二聚体进行的 CHELPG 布居分析确定。该二聚体所需的静电表面由使用 MP2 理论和 6 - 31g++(3df,3pd)基组进行的从头算计算确定。然后优化 LJ 参数，以便通过模拟能很好地重现液 - 气共存曲线、临界参数和蒸气压。在巨正则系综中使用直方图重加权蒙特卡罗模拟来确定丙酮 - 氯仿、丙酮 - 甲醇和氯仿 - 甲醇二元混合物的相图。本工作中开发的力场重现了实验中发现的丙酮 - 氯仿混合物中的最低压力共沸物。预测的共沸组成 x(CHCl3) = 0.77 与实验值 x(CHCl3)expt = 0.64 相当吻合。与常用于气 - 液平衡计算的其他力场相比，还发现新的力场能更好地预测丙酮 - 甲醇和氯仿 - 甲醇的压力 - 组成行为。在 300 K 和 1 bar 下对丙酮 - 氯仿、丙酮 - 甲醇和甲醇 - 氯仿的等摩尔混合物进行了 NPT 模拟。微观结构分析表明丙酮和氯仿之间存在显著的氢键。在丙酮 - 甲醇或氯仿 - 甲醇混合物中发现有限的种间氢键。
