Article révisé par les pairs
Résumé : Nonequilibrium molecular dynamics (NEMD) experiments measuring the shearing forces within an atomic fluid undergoing a planar Couette flow [Hoover, Ann. Rev. Phys. Chem. 34, 103 (1983); Evans and Morriss, Comp. Phys. Rep. 1, 299 (1984)] are performed by the subtraction method [Ciccotti et al., J. Stat. Phys. 21, 1 (1979)] at sufficiently low velocity gradient in order to remain within the linear response regime. The resulting stress averaged over many hundreds of NEMD trajectories (segments) and the stress-stress time autocorrelation function evaluated along the available equilibrium trajectory (required for the subtraction method), which are formally related by linear response theory, are shown to yield compatible estimations of the shear viscosity. This confirms the correct limiting behavior of the effective shear viscosity evaluated by similar NEMD experiments at much larger gradients. At the fluid state point far from the melting line that we consider, no size dependence of the viscosity is observed in both types of experiments. A comparison of the efficiency of both methods is not straightforward, as we found that, for a fixed number of time steps, the error estimated on the viscosity is independent of the system size for the Green-Kubo formula but decreases as N-0.5 in the NEMD case. © 1989 The American Physical Society.