How Large is the Elephant in the Density Functional Theory Room?

A recent paper reported highly accurate
density functional theory
results for atomization energies and dipole moments using a multiwavelet-based
method and compared the results with those obtained by standard Gaussian
basis sets of the aug-cc-pVXZ type. Typical errors with the large
aug-cc-pV5Z basis set were in the 0.2 kcal/mol range with outliers
displaying errors of ∼2 kcal/mol, and these results could be
taken as an indication that Gaussian basis sets in general are unsuitable
for achieving high accuracy. We show that by choosing Gaussian basis
sets optimized for density functional theory, basis set methods are
capable of achieving accuracy comparable to that from the multiwavelet
approach.