Towards a theoretical description of molecular junctions in the Coulomb blockade regime based on density functional theory

TL;DR

This paper explores the use of NEGF-DFT methods to describe electron transport in molecular junctions within the Coulomb blockade regime, demonstrating their potential accuracy despite traditional limitations.

Contribution

It provides a theoretical framework showing NEGF-DFT can predict Coulomb blockade addition energies accurately in simple model systems.

Findings

Coulomb blockade addition energies can be predicted with NEGF-DFT

The Kohn-Sham gap and derivative discontinuity issues are not critical

NEGF-DFT shows promise for Coulomb blockade regime analysis

Abstract

Non-equilibrium Greens function techniques (NEGF) combined with Density Functional Theory (DFT) calculations have become a standard tool for the description of electron transport through single molecule nano-junctions in the coherent tunneling regime. However, the applicability of these methods for transport in the Coulomb blockade (CB) regime is still under debate. We present here NEGF-DFT calculations performed on simple model systems in the presence of an effective gate potential. The results show that: i) the CB addition energies can be predicted with such an approach with reasonable accuracy; ii) neither the magnitude of the Kohn-Sham gap nor the lack of a derivative discontinuity in the exchange-correlation functional represent a problem for this purpose.