GEMC Simulation Of The Vapor Liquid Phase Equilibrium

With the rapid development of statistic mechanics theory and computer technology, computer molecular simulation has became a powerful tool to study the fluid in molecular level. Molecular simulation technology has also developed rapidly in chemical engineering field and became a useful means that the study of theory and experiment can be preceded.The Gibbs Ensemble Monte Carlo simulation that the result can be obtained faster than indirect computer simulation is a direct computer simulation method for simulating phase equilibrium. Furthermore, this kind of simulation is more convenient than indirect Monte Carlo simulation. In this paper, Gibbs Ensemble Monte Carlo simulation has been used successfully to simulate the vapor-liquid phase equilibrium for binary systems such as water/methane, water/carbon dioxide, ethane/heptane and octane/dodecane at a series of pressures and temperatures by computer program—Visual Fortran95. Lennard-Jones potential model, Buckingham Exp-6 potential model and Columbus potential function have been used respectively to calculate the short range potential energy among electric charges and the potential energy among molecules. At the same time,long-range corrections and Ewald Summation techniques have been used respectively to calculate no-charge long range intermolecular interactions and long range charge-charge interactions in the simulations.Compared the data got from computer simulation with experimental data, it shows that both of them are in good agreement with each other and the method is feasible. According to the paper, the experiences about studying the vapor-liquid phase equilibrium of more complicated hydrocarbon and the thermodynamics of more complicated mixture about water has been obtained.