Computer Simulation of the Characteristic Curves of Pure Fluids

Brown's characteristic curves (also known as ideal curves) describe states at which one thermodynamic property of a real pure fluid matches that of an ideal gas; these curves can be used for testing the extrapolation behavior of equations of state. In this work, some characteristic curves are computed directly without recourse to an equation of state for some pair potentials by Monte Carlo computer simulation. The potentials used are an ab initio potential for argon, the 1-center Lennard-Jones potential, and a softer pair potential whose short-range part is in accordance with quantum mechanical predictions. The influence of the short-distance repulsion on the characteristic curves is found to be significant even in the 10-100 MPa pressure range.