Figure : Electronic energies of each state in the concerted transition state (CTS) and biradical reaction pathways relative to the reactants. Four methods are shown: APC(6,6)-tPBE (green, this work), hand-selected (6,6)-tPBE (black), HF-PBE (blue), and reference MR-AQCC results (red). The structures of each transition state and intermediate are displayed on the right.