For relaxation of the polaron in TiO 2 , DC-PBE affords energetics in good agreement with MP2. For the PBE0 and SCAN functionals, however, the DC procedure wors-ens what had been favorable agreement with MP2 results. Because the cost of DC-DFT in periodic calculations will be similar to the cost of plain PBE0, we suggest that the role of DC-DFT should be a diagnostic one: where SIE problems are anticipated, DC-DFT provides an indication of whether defect delocalization is likely to persist as the fraction of exact exchange is adjusted. It does so without the need to altogether abandon any treatment of electron correlation. Analytic gradients afford the ability to describe structural relaxation with DC-DFT.