Molecular Conductance: Chemical Trends of Anchoring Groups

TL;DR

This study uses first-principles calculations to explore how different anchoring atoms and contact configurations affect molecular conductance in benzene-Au junctions, revealing chemical trends and contact-dependent behaviors.

Contribution

It provides a detailed first-principles analysis of how anchoring atoms and contact structures influence molecular conductance, highlighting the importance of atomic configuration.

Findings

Conductance decreases with increasing atomic number of anchoring atom for flat contacts.

Contact atomic configuration can alter the preferred anchoring atom at small bias.

Chemical trends in conductance depend on contact atomic details and bias conditions.

Abstract

Combining density functional theory calculations for molecular electronic structure with a Green function method for electron transport, we calculate from first principles the molecular conductance of benzene connected to two Au leads through different anchoring atoms -- S, Se, and Te. The relaxed atomic structure of the contact, different lead orientations, and different adsorption sites are fully considered. We find that the molecule-lead coupling, electron transfer, and conductance all depend strongly on the adsorption site, lead orientation, and local contact atomic configuration. For flat contacts the conductance decreases as the atomic number of the anchoring atom increases, regardless of the adsorption site, lead orientation, or bias. For small bias this chemical trend is, however, dependent on the contact atomic configuration: an additional Au atom at the contact with the (111) lead changes the best anchoring atom from S to Se although for large bias the original chemical trend is recovered.