Core-valence correlation consistent basis sets for second-row atoms (Al–Ar) revisited

The augmented tight-d cc-pV(n + d)Z (where n = D, T, Q, 5) basis sets are now the recommended “standard” correlation consistent basis set for second-row atoms. These revised sets, however, do not have a suitable corresponding core–valence basis set series to enable an assessment of core–valence corrections. This is particularly important when such effects are assessed and are used as an additive effect, as is done in composite methods. Thus, there is a need for a new “standard” core–valence series of basis sets for second-row atoms that builds systematically upon the cc-pV(n + d)Z sets. In this study, we develop the cc-pCV(n + d)Z basis set series and demonstrate their usefulness through molecular benchmark calculations for a series of second-row systems. These revised core–valence basis sets provide greater consistency in the description of core–valence effects with respect to change in basis set, enabling greater utility of the sets, even for the lower values of n.