GEMC和GDI方法计算流体气液相平衡的比较

考察采用TraPPE联合原子和OPLS全原子力场两种分子力场, Gibbs系综蒙特卡罗(GEMC)方法和Gibbs-Duhem积分(GDI)方法计算流体气液相平衡的适用性、计算速度、计算精度等问题. 结果表明, 在采用全原子力场情况下, GDI方法比GEMC方法极大地节省了计算时间. 从计算结果来看, 两种方法各有适用范围, 在使用时可互为补充. 在给定力场的前提下, 两种方法所得到的液相密度、蒸发焓、临界温度和临界密度相差不大, 而当力场中的缺陷导致蒸发焓的计算不够准确时, 两种计算方法得到的气体的压力和密度明显不同，进而导致预测的临界压力也明显不同.

Comparison of GEMC and GDI Methods in Prediction of the Fluid Vapor-liquid Equilibrium

TraPPE-UA and OPLS-AA force fields were used to investigate the applications of the Gibbs ensemble Monte Carlo (GEMC) method and the Gibbs-Duhemintegration (GDI) method in predicting the vapor-liquid equilibrium properties. It was found that the GDI method was much faster than the GEMC method if all-atom force field was employed. Based on the calculation results, the two methods could be viewed as complementary to the problem of vapor liquid coexistence. The calculated liquid densities, enthalpies of vaporization, critical temperatures, and critical densities by the two methods were very close to each other for a given force field. If the force field caused errors in the calculated heats of vaporization, the calculated vapor pressures and densities by the two methods were clearly different, which also led to difference in the predicted critical pressure.