On the wavevector dependent shear viscosity of a simple fluid

Non-equilibrium molecular dynamics (NEMD) simulations employing the sinusoi dal transverse force (STF) method are used to calculate the wavevector and strain rate dependent sheer viscosity of a WCG fluid at a zero wavevector n umber density of 0.8442, and zero wavevector temperature of 0.722. The func tional form of the dependence of shear viscosity on the strain rate and wav evector are examined, in the zero field limit. The ramifications of these r esults for the possible existence of the Burnett coefficients are discussed . The shear rate dependent viscosity for a range of wavevectors can be fitt ed to both a Cross analytical form and a formula derived from Quentrec`s lo cal order theory. Also it can be fitted to two square-root regimes. The ext rapolated zero strain rate viscosities are consistent with a Lorentzian fun ctional form, a Taylor series expansion in q(2) and also to a q(3/2) variat ion at low wavevector. This study reveals that with current computational r esources it is still not possible to establish the validity of the Burnett coefficients.