How Accurate Is Density Functional Theory at Predicting Dipole Moments? An Assessment Using a New Database of 200 Benchmark Values

Dipole
moments are a simple, global measure of the accuracy of
the electron density of a polar molecule. Dipole moments also affect
the interactions of a molecule with other molecules as well as electric
fields. To directly assess the accuracy of modern density functionals
for calculating dipole moments, we have developed a database of 200
benchmark dipole moments, using coupled cluster theory through triple
excitations, extrapolated to the complete basis set limit. This new
database is used to assess the performance of 88 popular or recently
developed density functionals. The results suggest that double hybrid
functionals perform the best, yielding dipole moments within about
3.6–4.5% regularized RMS error versus the reference valueswhich
is not very different from the 4% regularized RMS error produced by
coupled cluster singles and doubles. Many hybrid functionals also
perform quite well, generating regularized RMS errors in the 5–6%
range. Some functionals, however, exhibit large outliers, and local
functionals in general perform less well than hybrids or double hybrids.