醋酸乙烯的NVT-GEMC模拟研究

NVT-GEMC simulation on vinyl acetate

采用了NVT-Gibbs系综蒙特卡罗(NVT-GEMC)方法,借助于Towhee模拟软件,在常压下,温度为293.15 K～473.15 K条件下,对醋酸乙烯体系进行汽液相平衡模拟计算。采用力场参数迁移的方法将TraPPE-UA力场描述文件中缺少的与CHo=c原子基团相关的键参数和非键参数补全。在此基础上,通过设置合理的模拟参数,计算得到了常压下醋酸乙烯汽液相密度随温度的变化情况。将计算值与实验值进行对比,发现液相密度的计算值与实验值的相对偏差在低温时较小,约在10%以内;随温度的升高相对偏差逐渐变大,在473.15 K时高达25%。这说明GEMC方法模拟计算醋酸乙烯体系相共存性质具有可行性,TraPPE-UA力场中CHo=c原子的力场参数还有待修正。

NVT Gibbs ensemble Monte Carlo （NVT-GEMC） method is used to compute the vapor-liquid equilibrium of pure vinyl acetate under the condition of normal pressure and the temperature from 293.15 K to 473.15 K with TraPPE-UA force field and Towhee software. The bond and non-bond interaction parameters of missing atom CHo=c of vinyl acetate in TraPPE-UA force field were added by the method of force field parameters transfer. On that basis, the vapor and liquid phase density of vinyl acetate was simulated at different temperature at normal pressure with appropriate simulation parameters. Comparing the simulation results with the literature values, we can find that the relative deviation of liquid density between the simulated and literature value is lesser at low temperature, about 10 %; with the rise of temperature, the relative deviation gradually changes, which is as high as 25% at 473.15 K. This shows that GEMC method viably simulate phase coexistence properties for vinyl acetate system, and force field parameters for CHo=c in TraPPE-UA force field remain to be fixed.