THE EXP-6 POTENTIAL FLUID AT VERY HIGH-PRESSURES - COMPUTER-SIMULATIONS AND THEORY

The exp-6 potential fluids for four values of the softness parameter a lpha, ranging from 11.5 to 14.5, have been investigated both by comput er simulations and theory at supercritical temperatures and very high densities (pressures). Tables of the simulation data for pressure incl ude altogether 141 thermodynamic state points generated at six tempera tures for each alpha. In addition to computation of the thermodynamic properties, great attention has been paid to the structure, and an app roximate location of the onset of freezing has been determined. To est imate the properties of the fluid from theory, a modified version of t he Weeks-Chandler-Anderson (mWCA) theory and the optimized reference h ypernetted chain (RHNC) theory were used. It is shown that for the the rmodynamic properties mWCA theory performs very well under all stable fluid conditions considered, whereas RHNC theory, comparable with mWCA at the lower densities considered, gradually loses its accuracy in th e very high density range. However, for structure the overall performa nce of RHNC theory is considerably better than that of mWCA, which poi nts to possible cancellation of errors in the latter theory when appli ed to thermodynamic properties.