Effect of quadrupole moment on the phase behavior of binary mixtures containing ethene

Histogram-reweighting Monte Carlo simulations in the grand canonical ensemble are used to determine the effect of quadrupole moment on the phase behavior of binary mixtures containing ethene. Two united-atom force fields for ethene are developed, one with an explicit representation of the quadrupole moment via partial charges, the other without. Simulations demonstrate that the addition of an explicit quadrupole moment results in a slight improvement in the reproduction of pure ethene vapor-liquid equilibria. For mixtures of xenon/ethene, the predictions of simulation are also improved by the use of an explicit quadrupole moment. For CO2/ethane mixtures, however, the quadrupole explicit force field fails to predict the maximum pressure azeotrope found experimentally, while the force field without a quadrupole moment is in quantitative agreement with experiment. For n-butane/ethene mixtures the quadrupole moment has little effect on the predicted pressure composition behavior.