Bond Breaking and Bond Formation: How Electron Correlation is Captured   in Many-Body Perturbation Theory and Density-Functional Theory
  For the paradigmatic case of H2-dissociation we compare state-of-the-art many-body perturbation theory (MBPT) in the GW approximation and density-functional theory (DFT) in the exact-exchange plus random-phase approximation for the correlation energy (EX+cRPA). For an unbiased comparison and to prevent spurious starting point effects both approaches are iterated to full self-consistency (i.e. sc-RPA and sc-GW). The exchange-correlation diagrams in both approaches are topologically identical, but in sc-RPA they are evaluated with non-interacting and in sc-GW with interacting Green functions. This has a profound consequence for the dissociation region, where sc-RPA is superior to sc-GW. We argue that for a given diagrammatic expansion, the DFT framework outperforms the many-body framework when it comes to bond-breaking. We attribute this to the difference in the correlation energy rather than the treatment of the kinetic energy. 
Fabio Caruso, Daniel R. Rohr, Maria Hellgren, Xinguo Ren, Patrick   Rinke, Angel Rubio, and Matthias Scheffler
physics.chem-ph cond-mat.mtrl-sci