Considering augmented (diffuse) basis sets, we find that the DLPNO approximation behaves less systematically in these cases, and there are outliers when aug-cc-pVDZ is used (see Figs. and). Specifically, five of the S66 dimers exhibit DLPNO errors 1 kcal/mol at the RI-MP2/aug-cc-pVDZ level, which persist as the PNO thresholds are tightened but disappear in aug-cc-pVTZ and aug-cc-pVQZ calculations. Similar (albeit smaller) outliers arise using def2-SVPD but are absent using def2-TZVPD. Thus, there seems to be a peculiar instability problem with augmented double-ζ basis sets, which is not observed in basis sets of higher cardinality.