Revisiting the Stokes-Einstein relation without a hydrodynamic diameter

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We present diffusion coefficient and shear viscosity data for the Lennard-Jones fluid along nine isochores above the critical density, each involving a temperature variation of roughly two orders of magnitude. The data are analyzed with respect to the Stokes-Einstein (SE) relation, which breaks down gradually at high temperatures. This is rationalized in terms of the faet that the reduced diffusion coefficient 5 and the reduced viscosity ij are both constant along the system's lines of constant excess entropy (the isomorphs). As a consequence, Dij is a function of T /T Ref(p) in which Tis the temperature, pis the density, and T Ref(p) is the temperature as a function of the density along a reference isomorph. This allows one to successfully predict the viscosity from the diffusion coefficient in the studied region of the thermodynamic phase diagram.
Original languageEnglish
Article number021101
JournalJournal of Chemical Physics
Issue number2
Publication statusPublished - 10 Jan 2019

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