If DTQ points are calculated, Helgaker performs better than Martin4 for both augmented and non-augmented bases coupled with the CP correction, and provides energies that are more converged than if kept at the Q level only. However, when resorting to non-augmented/CP basis sets, the three-parameter schemes Martin46 (24), Feller (19) and Peterson (20) provide even smaller deviations than Helgaker, with Peterson surpassing the others. Because Martin4 and Helgaker are based on leading orders at large X (cf. Section II C 1), those are likely to deteriorate when considering the smallest cc-pVDZ basis set in the extrapolation sequence . Indeed, Martin4 and Helgaker in general produce slightly lower energies with respect to the PW references, but these deviate more widely from above when D points are considered (Fig. ). Thus, the fact that Peterson is the most appropriate for the non-augmented basis with DTQ points appears quite coincidental, and may also result from the lack of diffuse functions that causes additional BSIE not related to the description of the Coulomb cusp, but rather due to long-range effects which cannot be fully corrected for by GTO extrapolations .