The Influence of Molecular Adsorption on Elongating Gold Nanowires

TL;DR

This study uses molecular dynamics simulations to explore how different adsorbates influence the structural evolution and mechanical stability of elongating gold nanowires, revealing that adsorbates enhance ductility and structural motif formation.

Contribution

The paper demonstrates that molecular adsorbates significantly improve the formation of stable monatomic chains and helical structures in gold nanowires during elongation, a novel insight into nanowire mechanics.

Findings

Adsorbates increase ductile elongation of gold nanowires.

Formation of stable monatomic chains and helical structures is facilitated by adsorbates.

Weakly interacting species reduce mechanical stability of nanowires.

Abstract

Using molecular dynamics simulations, we study the impact of physisorbing adsorbates on the structural and mechanical evolution of gold nanowires (AuNWs) undergoing elongation. We used various adsorbate models in our simulations, with each model giving rise to a different surface coverage and mobility of the adsorbed phase. We find that the local structure and mobility of the adsorbed phase remains relatively uniform across all segments of an elongating AuNW, except for the thinning region of the wire where the high mobility of Au atoms disrupts the monolayer structure, giving rise to higher solvent mobility. We analyzed the AuNW trajectories by measuring the ductile elongation of the wires and detecting the presence of characteristic structural motifs that appeared during elongation. Our findings indicate that adsorbates facilitate the formation of high-energy structural motifs and lead to significantly higher ductile elongations. In particular, our simulations result in a large number of monatomic chains and helical structures possessing mechanical stability in excess of what we observe in vacuum. Conversely, we find that a molecular species that interacts weakly (i.e., does not adsorb) with AuNWs worsens the mechanical stability of monatomic chains.