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Nonempirical free volume viscosity model for alkane lubricants under severe pressures

: Falk, K.; Savio, D.; Moseler, M.

Preprint ()

Physical review letters 124 (2020), Nr.10, Art, 105501, 6 S.
ISSN: 0031-9007
ISSN: 1079-7114
Zeitschriftenaufsatz, Elektronische Publikation
Fraunhofer IWM ()
brownian motion; complex fluids; diffusion; dissipative dynamics; interparticle interactions; lubrication; Random Walks; rheological properties; rheology; self-diffusion; tribology

Viscosities η and diffusion coefficients Ds of linear and branched alkanes at pressure 0 smaller than P smaller than 0.7  GPa and temperature T=500–600  K are calculated from molecular dynamics simulations. Combining Stokes-Einstein, free volume, and random walk concepts results in an accurate viscosity model for the considered P and T. All model parameters (hydrodynamic radius, random walk step size, and step frequency) are extracted from equilibrium molecular dynamics via microscopic ensemble averages rendering η(P,T) a parameter-free predictor for lubrication simulations.