The distributions of both δ RI and ∆RI for the DZ quality basis sets are shown in Figure as violin plots. It can be seen that both error metrics change significantly when the cc-pVDZ-PP-F12-OptRI basis is used for the anion of the atom (middle distribution in each panel), but the error distributions resulting from the new aug-cc-pVDZ-PP-F12-OptRI set for the anion (rightmost distribution) closely resemble those when cc-pVDZ-PP-F12-OptRI is used for the neutral atom (leftmost), which meets the qualitative aim outlined above and hence indicates that a similar quality of RI approximation for the anion as for the neutral atom. Violin plots of the RI errors at the TZ and QZ level are presented in Supplementary