Efficient DFT+U calculations of ballistic electron transport: Application to Au monatomic chains with a CO impurity

TL;DR

This paper introduces an efficient DFT+U method for calculating electron transport in open quantum systems, applied to gold chains with CO impurities, improving the accuracy of conductance predictions by correcting spurious effects.

Contribution

The paper presents a simplified approach to incorporate Hubbard U in DFT+U calculations for transport, applied to Au chains with CO, enhancing realism in conductance modeling.

Findings

Hubbard U removes spurious magnetization in Au chains.

Conductance with CO is significantly reduced at the atop site.

DFT+U yields a more realistic conductance of 1 G_0 for Au chains.

Abstract

An efficient method for computing the Landauer-Buettiker conductance of an open quantum system within DFT+U is presented. The Hubbard potential is included in electronic structure and transport calculations as a simple renormalization of the non-local pseudopotential coefficients by restricting the integration for the on-site occupations within the cutoff spheres of the pseudopotential. We apply the methodology to the case of an Au monatomic chain in presence of a CO molecule adsorbed on it. We show that the Hubbard U correction removes the spurious magnetization in the pristine Au chain at the equilibrium spacing, as well as the unphysical contribution of d electrons to the conductance, resulting in a single (spin-degenerate) transmission channel and a more realistic conductance of 1 G_0 . We find that the conductance reduction due to CO adsorption is much larger for the atop site than for the bridge site, so that the general picture of electron transport in stretched Au chains given by the local density approximation remains valid at the equilibrium Au-Au spacing within DFT+U.