Liquid CH4, liquid CF4and the partially miscible liquid mixture CH4/CF4

Abstract

The partially miscible liquid mixture CH₄/CF₄ was simulated using molecular dynamics calculations based on one-centre Lennard-Jones (LJ) potential functions and four-centre LJ potentials. The calculations with the latter potential model were performed with a fully vectorized molecular dynamics program exploiting constraints for the solution of the equations of motion for the molecules. The simulated static and dynamic properties of both the mixtures and the pure liquids are reasonably comparable with those of the real systems. Particularly, the phase separation of the mixture occurs in the range where it is observable in the real CH₄/CF₄ mixture. Given the limited test of the present study, both potential models are equally suitable for the simulation of this non-ideal mixture, where the unlike interaction parameters are chosen as proposed in [1]. However, while the spherically symmetric potential gives better pressures, the four sites potential model is preferable for the dynamic quantities in comparison with experiment. This is in good agreement with earlier simulation studies on other molecular systems.