R05a and R05b refer to the two symmetry-unique molecular conformations found in the R05 polymorph. In the self-consistent DFT calculations, shown in the left panel of Fig. (a), all the dispersion-corrected GGA and meta-GGA functionals perform very poorly, over-stabilizing the red and orange conformers over the yellow ones by several kJ/mol. This can be understood as a SIE artifact, as discussed above. PBE+D3 shows the worst performance, completely reversing the energetic ordering relative to CCSD(T). Hybrid functionals partially mitigate the effect of SIE and behave better than the GGA functionals, and the hybrid meta-GGA functional SCAN0+D3 emerges as the best performer amongst the set of functionals tested here, although it still does not reproduce the CCSD(T) energy ordering. DC-DFT results for ROY are shown in the middle section of Fig. , for the same set of functionals. The DC procedure improves upon the self-consistent DFT results in all cases, coming much closer to the correct energetic ordering except in a few quasi-degenerate cases. This validates the hypothesis that π-delocalization error drives the erratic and mostly erroneous results obtained using conventional DFT. Lowest-and highest energy conformers are correctly predicted by DC-DFT for all functionals tested here, and the three lowest-energy conformers are correctly predicted by all of the DC-DFT methods except for DC-PBE+D3. Failure of the latter approach may be a sign of larger functional-driven error as compared to the hybrid functionals to the SCAN meta-GGA functional. Even for PBE+D3, however, the DC procedure moves the results closer to the correct energetic ordering as compared to the corresponding self-consistent DFT calculation. The DC-SCAN0+D3 and DC-PBE0+D3 methods afford correct energetic ordering for the most of the conformers, as judged by comparison to CCSD(T) benchmarks. The success of DC-SCAN and DC-SCAN0 has been noted in unrelated work. Having identified SCAN+D3 and SCAN0+D3 as the best of the self-consistent DFT approaches for the ROY molecule, let us return to the one-dimensional potential energy scans in Fig. . Both DC-SCAN+D3 and DC-SCAN0+D3 perform well in comparison to benchmark CCSD(T) calculations from Ref. 26, although neither is quite as faithful to the benchmark as is SCS-MP2D. In contrast, the self-consistent SCAN+D3 and SCAN0+D3 calculations yield erroneously large rotational barriers around 40-90 • , as structures with angles of 0-30 • are over-stabilized due to the SIE. Torsional energy profiles computed using (DC-)B3LYP+D3 and (DC-)PBE0+D3 are shown in Fig. and exhibit most of the same trends that are seen for the hybrid (DC-)SCAN0+D3 level of theory in Fig. . Thus, the good performance of DC-SCAN+D3 and DC-SCAN0+D3 is not simply a matter of choosing a good functional to correct; the correction itself improves the results substantially.