Fig. 1: Viscosity, particle motion, and collective shear dynamics in liquids.
From: Atomistic mechanisms of viscosity in 2D liquid-like fluids
a The shear viscosity η determines the macroscopic resistance to shear flow in fluids. b A local configurational excitation consisting in losing or gaining one neighbor. τLC, the lifetime of local connectivity, is the average timescale associated to this microscopic process. c Structural rearrangements in liquids are governed by localized events in which one or few particles hop a potential barrier (ΔG), as assumed in Eyring and Frenkel theories of liquid viscosity. This activated process happens with an averaged rate \({\tau }_{F}^{-1}\), where τF is the microscopic Frenkel time. d Collective shear waves in liquids propagate only up to a length-scale l ~ 1/kg, with kg the wave-vector gap in their dispersion. According to Maxwell viscoelasticity theory, kg ~ 1/(CTτM) where CT is the high-frequency speed of propagation for shear waves and τM is the collective Maxwell relaxation time. Panel (a) is created with the help of ChatGPT.
