Of the ∼ 0.2 Ha of energy lowering that is obtained at the PBE level when the HF-optimized starting structure is relaxed (Fig. ), comparison to the DC-PBE result suggests that about half of that amount is density-driven error. In the PBE0 optimization, the difference between PBE and DC-PBE is much smaller, consistent with the idea that the density-driven error has been reduced because a hybrid functional is used for the optimization. Shifts between DFT and DC-DFT are plotted in Fig. for two functionals and two optimization trajectories, demonstrating that the shift for PBE0 is consistently smaller than that for PBE, as a result of smaller density-driven error in the hybrid functional.