Deviations from Arrhenius dynamics in high temperature liquids, a possible collapse, and a viscosity bound

Liquids realize a highly complex state of matter in which strong competing kinetic and interaction effects come to life. As such, liquids are more challenging understand than either gases or solids generally. In weakly interacting gases, the dominate. By contrast, low temperature typically feature far smaller fluctuations about their ground state. Notwithstanding complexity, with exception quantum fluids supercooled liquids, various aspects common liquid dynamics such as dynamic viscosity often assumed be given by rather simple, Arrhenius-type, activated forms nearly constant (i.e., independent) energy barriers. this work, we analyze experimentally measured viscosities numerous above equilibrium melting see how well assumption fares. We find, for investigated marked deviations from simple dynamics. Even temperatures, drops, these increases strongly predicted dominated single uniform barrier. For metallic fluids, scale prefactors best Arrhenius fits is consistent that product $nh$ $n$ number density $h$ Planck's constant. examined, constitutes lower bound on viscosity. find scaling axis (complementing viscosity) leads partial collapse dependent different fluids; allows functional dependence includes yet general form alone. speculate relations between non-Arrhenius thermodynamic observables.