MOLECULAR-DYNAMICS EQUATION OF STATE FOR NONPOLAR GEOCHEMICAL FLUIDS

Remarkable agreement between molecular dynamics simulations and experimental measurements has been obtained for methane for a large range of intensive variables, including those corresponding to liquid/vapor coexistence. Using a simple Lennard-Jones potential the simulations not only predict the PVT properties up to 2000 degrees C and 20,000 bar with errors less than 1.5%, but also reproduce phase equilibria well below 0 degrees C with accuracy close to experiment. This two-parameter molecular dynamics equation of state (EOS) is accurate for a much larger range of temperatures and pressures than our previously published EOS with a total fifteen parameters or that of Angus et al. (1978) with thirty-three parameters. By simple scaling, it is possible to predict PVT and phase equilibria of other nonpolar and weakly polar species.