Equation of state for the Lennard-Jones fluid

Abstract

Molecular dynamics calculations of the pressure and configurational energy of a Lennard-Jones fluid are reported for 108 state conditions in the density range 0·35 ≦ ρ* ≦ 1·20 and temperature range 0·5 ≦ T* ≦ 6 (where ρ* = ρσ3, T* = kT/ε). Particular attention is paid to the dense fluid region (ρ* ≧ 0·9), including state conditions in the subcooled liquid region. These new simulation results for P and U are combined with those of previous workers, together with low density values calculated from the virial series and values of the second virial coefficients themselves, to derive an equation of state for the Lennard-Jones fluid that is valid over a wide range of temperatures and densities. The equation of state used is a modified Benedict-Webb-Rubin equation having 33 constants. It fits the data well over the density range 0 ≦ ρ* ≦ 1·2 and for T* values ranging from 0·5 to 6·0 (the exact temperature range depending to some extent on the density considered). We also calculate for the same range of state conditions, certain two- and three-body integrals (J, K and L) that occur in perturbation theory for molecular fluids. An interpolation formula is presented for the estimation of these integrals.