Shear viscosity and thermal conductivity of quadrupolar real fluids from molecular simulation

Abstract

In the present work, equilibrium molecular dynamics was used with the Green-Kubo formalism to simultaneously calculate shear viscosity and thermal conductivity of ten real fluids, i.e. F₂, N₂, O₂, CO₂, C₂H₆, C₂H₄, C₂F₆, C₃H₄, C₃H₆ and SF₆. The fluids were consistently described by the two-center Lennard–Jones plus point quadrupole (2CLJQ) pair potential, whose parameters were adjusted to vapor–liquid equilibria only [J. Phys. Chem. B, 2001, 105, 12126–12133]. The predicted shear viscosities and thermal conductivities show an overall average deviation of only about 10% from correlations of experimental data where comparison was possible.

At low temperature and high density state points, the Green–Kubo integral for shear viscosity shows slow convergence. This problem can be overcome by a new approach developed in the present work. It is based on the adjustment of a suitable function describing the long time behavior of the autocorrelation function and yields reliable results without the need of excessively long simulation runs.

Keywords:

• Shear viscosity
• Thermal conductivity
• Green–Kubo
• Molecular simulation