Study of transport properties of a molecular junction as a function of distance between the leads

TL;DR

This study investigates how the transport properties of a benzene dithiol molecular junction change with lead separation, revealing optimal configurations and their impact on conductance.

Contribution

It provides an ab initio analysis of the optimal molecular configurations based on lead distance, highlighting a transition from symmetric to asymmetric bonding.

Findings

For distances longer than 12 Å, the molecule prefers asymmetric bonding.

At shorter distances, the molecule sits centrally between leads.

Configuration affects the transport properties of the junction.

Abstract

We consider a model of a molecular junction made of BDT (benzene dithiol) molecule trapped between two Au(100) leads. Using the ab initio approach implemented in the SIESTA package we look for the optimal configuration of the molecule as a function of a distance between the leads. We find that for the distance long enough the energy of the system is minimized when the molecule is bonded asymmetricaly, i.e. chemisorbed to one of the leads, whereas for the distance shorter than 12 \AA the energy is minimized for the molecule sitting in the middle between the leads. We discuss possible consequences of the above findings for the transport properties of the junction.