A Theoretical Study on the Equation of State of Liquid Methane at High Temperature and High Densities

Equation of state and molecular dissociation reactions of liquid methane at high-temperature and high-pressure are investigated by Statistical Mechanics and Chemical Equilibrium method, with focus on the interactions between CH4 and H2, which apparently would affect the equilibrium of chemical reactions and EOS of shock compressed liquid methane. By using a set of optimized exp-6 potential parameters obtained from experimental Hugoniot data (pH, V), our theoretical calculation results agree satisfactorily with published experimental data. The repulsive part of our potential, however, is softer than that determined by ideal mixture rule, which implies attractive interaction between CH4 and H2 may exist under high pressure. The effect of the effective potential between CH4-H2 on the dissociation of CH4 molecules under shock compression is also discussed in this paper.