Abstract
Prediction of molecular junction transport properties is a challenging task. One particularly complicated aspect of the problem is accurate description of binding between the molecule and the electrodes.
Effect of image charges and non-ground state properties of the molecule-electrode system are expected to induce significant error when using DFT to evaluate the junction properties. GW is a post-DFT method that is assumed to fix some of the problems of bare DFT approach.
In this contribution, we explore the (size) convergence properties of spectrum of sodium clusters using GW, and compare it to predictions by DFT and HF. We discuss the strategies to remove quasi-degeneracies induced by symmetries of the clusters, and their impact on critical properties of the spectrum, namely gap and average level spacing.
Our analysis serves as a guide towards convergence studies of molecular junctions using GW.