Influence of the repulsive coefficient α and approximate corresponding states in Mie α-6 and exponential α-6 fluids

Non-equilibrium molecular dynamics (NEMD) simulations of the Mie α-6 and the exponential α-6 (exp α-6) fluids have been carried out for 42 thermodynamic states. Various repulsive coefficients have been studied, α ranging from 9 to 14 for the Mie α-6 potentials and from 11 to 16 for the exp α-6 ones, which corresponds to a total of 603 points of simulation of stable phases. The simulations have shown that, for a given set of reduced temperature and density (using an appropriate scaling procedure), the reduced pressure varies linearly with α-6 for the Mie α-6 potentials and with α-7 for the exp α-6 potentials. Concerning the viscosity, it is shown that, for both potential families, the variation is linear with α. Thus, an approximate corresponding states scheme exists on pressure and on viscosity for fluids modelled by both potentials families, but only for each property separately. In addition, it appears that, approximate corresponding states exist between fluids modelled by a Mie α-6 potential and an exp (α + 2)-6 one for pressure, and between fluids modelled by a Mie α-6 potential and an exp (α + 2.5)-6 one for viscosity. So, despite obvious similarities, the influence of the shape of the potential on pressure and on viscosity is not strictly the same. Hence, a complete perfect corresponding states scheme (including both the pressure and the viscosity) seems hardly feasible between fluids modelled by the Mie α-6 and the exp α-6 potential families.