Diffuse functions
should be used (augmented basis sets in the case of Dunning's
correlation consistent basis sets such as cc-pvdz, aug-cc-pvdz).
However, Rinderspacher and Schreiner [52] emphasized that the
balanced nature of the basis set is the important aspect. Concerning
the basis set, in the recent study of Hedegård et al. [53] it was
shown that the aug-cc-pvdz basis set often led to significant deviations
from the basis set limit. This is in contrast to the study of
Grimme et al. [54]. Since the more recent study used a larger
number of molecules, it is likely that the often recommended usage
of basis sets with diffuse functions must still be handled with
caution.