Effect of stretching on the ballistic conductance of Au nanocontacts in presence of CO: a density functional study

TL;DR

This study uses density functional theory to analyze how stretching affects the ballistic conductance of gold nanocontacts with CO adsorption, revealing that the adsorption site significantly influences conductance behavior.

Contribution

It demonstrates that the bridge adsorption site explains conductance evolution during stretching, aligning with experimental data, and compares different nanocontact geometries for robustness.

Findings

Bridge site adsorption yields conductance around 0.6 G0.

Atop site adsorption suppresses conductance.

Conductance evolution matches experimental trends when considering the bridge site.

Abstract

CO adsorption on an Au monatomic chain is studied within density functional theory in nanocontact geometries as a function of the contact stretching. We compare the bridge and atop adsorption sites of CO, finding that the bridge site is energetically favored at all strains studied here. Atop adsorption gives rise to an almost complete suppression of the ballistic conductance of the nanocontact, while adsorption at the bridge site results in a conductance value close to 0.6 G0, in agreement with previous experimental data. We show that only the bridge site can qualitatively account for the evolution of the conductance as a function of the contact stretching observed in the experimental conductance traces. The numerical discrepancy between the theoretical and experimental conductance slopes is rationalized through a simple model for the elastic response of the metallic leads. We also verify that our conductance values are not affected by the specific choice of the nanocontact geometry by comparing two different atomistic models for the tips.