Monte Carlo Simulation Of The Vapor Liquid Phase Equilibrium For Linear Molecules And Mixture

The constant-NVT canonical ensemble Monte Carlo method has been used to simulate the phase equilibrium of linear molecule in this text. The simulated objects are made up of two mono-component substances and a mixture . The simulation program is written with FORTRAN on the base of the spherical molecular model. In the simulation, Widom test particle method is adopted to get the chemical potential and the Lennard-Jones model is chosen to calculate the potential energy of the system. The simulation is performed in a system of 256 molecules beginning with the model of face-centered cubic structure. The emphasis of the simulation is to set up with potential energy model for linear molecule. There are several Lennard-Jones interaction sites in every molecule. In order to depict the interaction between interaction sites accurately, some techniques must be adopted in the simulation such as the periodic boundary conditions, spherical potential truncation and the long range corrections. The Monte Carlo simulation program of the linear molecule model is written with full consideration for the possible overlap between the sites in the molecules. The simulation program for the mixture is written by improving the mono-component program, adopting proper mixing rule and the calculation method of the chemical potential. Ethane and n-butane are simulated at six different temperatures, However, the temperature for the binary mixture is 298.15K. The properties of the phase equilibria for these systems are simulated and the phase diagrams are drawn up. Results of the simulation show good agreement with the data in the literatures.Although the Monte Carlo method lies in some shortcomings such as calculating time is relatively long and there are so many controlling parameters in the simulation, the applied extension of the method is quite extensive. It is useful for even every linear molecule. Our works has paved the way for researching long chain-like molecules and polymer molecules in the future.