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Updated: Jul 14, 2026

The Diffusion of Passive Tracers in Laminar Shear Flow
Published on: May 1, 2018
Transport and Helfand moments in the Lennard-Jones fluid. I. Shear viscosity
S Viscardy1, J Servantie, P Gaspard
1Center for Nonlinear Phenomena and Complex Systems, Université Libre de Bruxelles, Campus Plaine, Code Postal 231, B-1050 Brussels, Belgium.
Abstract:
The authors propose a new method, the Helfand-moment method, to compute the shear viscosity by equilibrium molecular dynamics in periodic systems. In this method, the shear viscosity is written as an Einstein-type relation in terms of the variance of the so-called Helfand moment. This quantity is modified in order to satisfy systems with periodic boundary conditions usually considered in molecular dynamics. They calculate the shear viscosity in the Lennard-Jones fluid near the triple point thanks to this new technique. They show that the results of the Helfand-moment method are in excellent agreement with the results of the standard Green-Kubo method.
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