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.