Nanoscale sliding friction versus commensuration ratio

TL;DR

This study uses molecular dynamics to explore how the phononic friction coefficient varies with substrate-adsorbate commensuration and temperature in a one-dimensional model, revealing complex dependencies and regions of minimal friction.

Contribution

It provides new insights into the relationship between sliding friction, substrate topology, and temperature, highlighting the non-trivial dependence on commensuration ratio.

Findings

$ta_{ph}$ depends quadratically on substrate corrugation amplitude.

$ta_{ph}$ varies non-trivially with commensuration ratio.

A broad region of low $ta_{ph}$ exists for ratios between 0.6 and 0.9.

Abstract

The pioneer work of Krim and Widom unveiled the origin of the viscous nature of friction at the atomic scale. This generated extensive experimental and theoretical activity. However, fundamental questions remain open like the relation between sliding friction and the topology of the substrate, as well as the dependence on the temperature of the contact surface. Here we present results, obtained using molecular dynamics, for the phononic friction coefficient ($\eta_{ph}$) for a one dimensional model of an adsorbate-substrate interface. Different commensuration relations between adsorbate and substrate are investigated as well as the temperature dependence of $\eta_{ph}$. In all the cases we studied $\eta_{ph}$ depends quadratically on the substrate corrugation amplitude, but is a non-trivial function of the commensuration ratio between substrate and adsorbate. The most striking result is a deep and wide region of small values of $\eta_{ph}$ for substrate-adsorbate commensuration ratios between $\approx 0.6-0.9$. Our results shed some light on contradictory results for the relative size of phononic and electronic friction found in the literature.