Multicoefficient density functional theory (MC-DFT).

We have systematically tested the performance of several pure and hybrid versions of density functional methods on different types of molecular energies by combining energies calculated using more than one basis sets. Most hybrid functionals show important performance improvement as compared to methods using only a single basis set. The results suggest that, in many cases, scaling the basis set corrections is also important for density functional theory calculation. The best method, the B1B95 functional using the cc-pVDZ/cc-pVTZ/aug-cc-pVDZ basis set combination, achieves an average accuracy of 1.76 kcal/mol on a database of 109 atomization energies, 38 hydrogen-transfer barrier heights, 38 non-hydrogen-transfer barrier heights, 13 ionization potentials, and 13 electron affinities.