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Universality of the shear viscosity of alkali metals

Abstract : The universality of the shear viscosity of alkali metals is studied up to high pressure. Equilibrium moleculardynamics simulations are used to calculate the stress autocorrelation function, which allows us to obtain the valueof shear viscosity using the Green-Kubo formula. Atomic interactions are computed from Fiolhais pseudopotentialand are validated by comparison between pair distribution functions and mean-squared displacements obtainedfrom classical andab initiomolecular dynamics simulations. The description of the interactions is accurate atleast up to 12 GPa, 9.4 GPa, 6.6 GPa, and 3 GPa for Na, K, Rb, and Cs, respectively, and to a lesser extent upto 4.8 GPa for Li. A good agreement between simulation and experimental viscosity results along the liquid-gascoexistence curve is found. The viscosity appears to be a universal property over a wide range of the liquid phaseof the phase diagram, between 0.85 and 1.5 times the ambient melting density and up to seven times the ambientmelting temperature. Scaling laws are proposed following relations formulated in [Meyer, Xu, and Wax,Phys.Rev. B93,214203(2016)] so that it is possible to predict the viscosity value of any alkali metal with an accuracybetter than 10% over the corresponding density and temperature range.
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https://hal.univ-lorraine.fr/hal-02921763
Contributor : Jean-François Wax <>
Submitted on : Tuesday, August 25, 2020 - 2:52:41 PM
Last modification on : Thursday, February 25, 2021 - 10:10:55 AM

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Nadège Meyer, Hong Xu, Jean-François Wax. Universality of the shear viscosity of alkali metals. Physical Review B, American Physical Society, 2017, 96 (9), pp.094201. ⟨10.1103/PhysRevB.96.094201⟩. ⟨hal-02921763⟩

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