GEO s To illustrate the quantities of Eq. 11, we take a butadiene molecule as an example. In Figure , we rank the approximations within AVQZ based on their GEO s values. In the same plot, we also show |∆ A + ∆ C | and |∆ A | (note the log-scale in the y-axes). From this figure we can see that |∆ A | is negligible relative to GEO s , and that ∆ A + ∆ C sum also accounts only for a small fraction of GEO . This means that most of GEO can be directly linked and partitioned into the contributions from the errors in specific geometric parameters. This breakdown for the same butadiene molecule is shown in Figure . Based on Eq. 9, we partition GEO s into contributions from errors in the single and double bond lengths and the remainder of GEO s here is due to the errors in the angles (the sum of contributions from both bond and torsion angles ). We can also see how these GEO s components vary as we change the basis sets: AVQZ (left panel), AVTZ (middle panel), and AVDZ (right panel). The contribution from the angles is small for all approximations and basis sets. The GEO weights do not change substantially as we go from AVQZ to AVTZ as it is the case with the total GEO values. Interesting patterns and grouping of functionals can be observed based on their GEO contributions. At the AVQZ and AVTZ level, we can see that the single-bond contribution strongly dominates old-school (semi)local functionals (LDA, BLYP, PBE, TPSS). The situation is different in the case of hybrids, for most of which a double-bond contributions strongly dominates their GEO . As we go from AVTZ to AVDZ the relative contributions to GEO change strikingly and so do the rankings of approximations. An immediate noticeable change is that the light blue colour becomes more dominant in the AVDZ bars, indicating a more significant contribution from the errors in single-bond lengths. This change in the basis also reverses the trends in hybrids, where the contribution from singlebonds dominates over that of the double-bonds. On the other hand, a single-bond contribution still dominates GEO of PBE, TPSS and BLYP, with the difference that GEO of these functionals within AVDZ bears a substantial doublebond contribution. As observed earlier, the ge- The decomposition of GEO s for the butadiene molecule into the angle, double bond, and single bond components (Eq. 9). The three panels show the results within different basis sets: AVQZ (left), AVTZ (center), AVDZ (right). The approximations in all three panels are are ranked by their AVQZ GEO s values (left panel). ometric performance of HF gets drastically better as one goes from AVTZ to AVDZ and we can see here that this change in the basis substantially reduces both single-and double-bond contributions to its GEO . At the AVDZ basis, HF gets beaten here only by M06-2X, which also contains a large amount of exact exchange (54%).