Regularization of the slip length divergence in water nanoflows by inhomogeneities at the Angstrom scale

TL;DR

This study uses molecular dynamics simulations to show that static atomic-scale surface inhomogeneities, rather than wall dynamics, regularize the slip length divergence in water nanoflows, enabling no-slip conditions even on ideal surfaces.

Contribution

It reveals that static surface inhomogeneities at the Angstrom scale, not dynamic wall effects, control slip length regularization in water nanoflows.

Findings

Atomic displacements at Angstrom scale remove slip length divergence.

Surface thermal fluctuations suffice to generate these displacements.

No-slip condition can be achieved on ideal, smooth surfaces.

Abstract

We performed non-equilibrium Molecular Dynamics simulations of water flow in nano-channels with the aim of discriminating {\it static} from {\it dynamic} contributions of the solid surface to the slip length of the molecular flow. We show that the regularization of the slip length divergence at high shear rates, formerly attributed to the wall dynamics, is controlled instead by its static properties. Surprisingly, we find that atomic displacements at the Angstrom scale are sufficient to remove the divergence of the slip length and realize the no-slip condition. Since surface thermal fluctuations at room temperature are enough to generate these displacements, we argue that the no-slip condition for water can be achieved also for ideal surfaces, which do not present any surface roughness.