Rapid onset of molecular friction in liquids bridging between the atomistic and hydrodynamic pictures
- Friction in liquids arises from conservative forces between molecules and atoms. Although the hydrodynamics at the nanoscale is subject of intense research and despite the enormous interest in the non-Markovian dynamics of single molecules and solutes, the onset of friction from the atomistic scale so far could not be demonstrated. Here, we fill this gap based on frequency-resolved friction data from high-precision simulations of three prototypical liquids, including water. Combining with theory, we show that friction in liquids emerges abruptly at a characteristic frequency, beyond which viscous liquids appear as non-dissipative, elastic solids. Concomitantly, the molecules experience Brownian forces that display persistent correlations. A critical test of the generalised Stokes–Einstein relation, mapping the friction of single molecules to the visco-elastic response of the macroscopic sample, disproves the relation for Newtonian fluids, but substantiates it exemplarily for water and a moderately supercooled liquid. The employed approach is suitable to yield insights into vitrification mechanisms and the intriguing mechanical properties of soft materials.
Author: | Arthur StraubeORCiD, Bartosz G. Kowalik, Roland R. Netz, Felix HöflingORCiD |
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Document Type: | Article |
Parent Title (English): | Commun. Phys. |
Volume: | 3 |
First Page: | 126 |
Publisher: | Nature |
Date of first Publication: | 2020/07/10 |
DOI: | https://doi.org/10.1038/s42005-020-0389-0 |
Licence (German): | Creative Commons - CC BY - Namensnennung 4.0 International |