Study The Vapor-Liquid Equilibria Of Fluids Through Molecular Simulation

Chemical engineering workers eagerly need to research microscopic configurations, macroscopic thermodynamic properties and transportation properties of fluids on molecular level. Macroscopic thermodynamic properties of fluids can be obtained through researching microscopic properties of systems by computer simulation of molecules that has increasingly become the third method which can be comparable with experimental research and theoretic research in the field of understanding physical laws of thermodynamic systems. Both of Gibbs Ensemble Monte Carlo simulation methodology and Configurational-bias Monte Carlo simulation methodology are the methods of trying to search rational configurations of systems in nature. In this paper,Gibbs Ensemble Monte Carlo simulation combined with Configurational-bias Monte Carlo simulation has been used successfully to simulate the vapor-liquid phase equilibrium for pure H2O and binary mixtures n-C7H16/ n-C5H12, n-C7H16/ n-C6H14, CO2/ CH3OCH3, CO2/C3H8 and CO2/CH3COCH3 at a series of pressures and temperatures. In addition, the radial distribution function of pure water at 300K has also been calculated by indirect constant NVT Monte Carlo simulation. In simulation, No-charge short range intermolecular interactions and charge-charge short range interactions were calculated respectively by Lennard-Jones potential function(or Buckingham Exp-6 potential function) and Columbian potential function. No-charge long range intermolecular interactions and charge-charge long range interactions were calculated respectively by the method presented by Theodorou and Suter and Ewald summation technology. All molecular models were generated by using Configurational-bias Growth Methods. All simulation results show fair agreement with experimental data in the references. The simulation methods and techniques in the paper can be used to forecast the vapor-liquid phase equilibrium for binary mixture systems that are not so complicated. At the same time, the good basis for the simulation of more complicated molecular structure fluid systems in industry has been built up.