Investigation of the vapor-liquid equilibrium and supercritical phase of pure methane via computer simulations

The Gibbs Ensemble Monte Carlo (GEMC) simulation technique was used to study the vapor-liquid equilibrium (VLE) of pure methane in a wide range of thermodynamic state points. The properties of the pure fluid were also studied at supercritical (SC) conditions by performing NVT and NPT molecular dynamics (MD) simulations. Previously developed intermolecular potential models were employed to model the fluid and their properties were obtained and compared with available experimental data. The simulations have shown that a simple one site Lennard-Jones (LJ) potential model [B. Saager and J. Fischer, Fluid Phase Equil. 57 (1990) 35, J. Fischer, R. Lustig, H. Breitenfelder_Manske and W. Lemming, Mol. Phys. 52 (1984) 485.] provides accurate descriptions of the VLE state points. It is also suggested that for the accurate description of the fluid properties at SC conditions, one needs to employ all-atom (AA) interaction potentials to model the system. The effectiveness of such kind of potential models used in this study has been presented and discussed.