Shear viscosity in diatomic fluids

Abstract

The centre of mass interaction force between a pair of homonuclear diatomic molecules is expanded as a Taylor series in the bond vectors. This leads to terms in an expression for the off-diagonal stress tensor components which explicitly involve the molecular orientations. Stress correlation functions and steady state shear viscosities obtained using the expansion to only second order compare favourably with exact molecular dynamics results for moderately anisotropic molecules such as nitrogen over a range of liquid densities.