The Puzzling Stability of Monatomic Gold Wires

TL;DR

This paper investigates the stability of monatomic gold wires, combining theoretical methods to understand why they remain stable despite predictions of instability, highlighting a discrepancy between theory and experiment.

Contribution

It provides a comprehensive theoretical analysis of monatomic gold wire stability, exploring reasons for experimental stability that contradict existing computational predictions.

Findings

Thermodynamic tip suction explains wire thinning and stretching.

Calculations suggest the wire should be unstable against breaking.

Discussions propose possible reasons for the observed stability.

Abstract

We have examined theoretically the spontaneous thinning process of tip-suspended nanowires, and subsequently studied the structure and stability of the monatomic gold wires recently observed by Transmission Electron Microscopy (TEM). The methods used include thermodynamics, classical many-body force simulations, Local Density (LDA) and Generalized Gradient (GGA) electronic structure calculations as well as ab-initio simulations including the two tips. The wire thinning is well explained in terms of a thermodynamic tip suction driving migration of surface atoms from the wire to the tips. For the same reason the monatomic wire becomes progressively stretched. Surprisingly, however, all calculations so far indicate that the stretched monatomic gold wire should be unstable against breaking, contrary to the apparent experimental stability. The possible reasons for the observed stability are discussed.