Performance of density functionals with small split valence basis sets

Though there have been many studies of density functional theory and various density functionals for large basis sets, there have been extremely limited studies of DFT with smaller basis sets. This paper discusses the ability of a series of density functionals to reproduce experimental heats of formation at the 3-21G*, 3-21+G*, and MIDI! basis sets. Also included are G3, G3MP2, MNDO, and PM3 calculations for comparison purposes. Good results for 3-21G* were obtained using mPW exchange with gradient-corrected correlation functionals LYP, PBEc, and PW91c, and 3-21+G* performed well with PBEx and PW91x exchange functionals when coupled with these same gradient-corrected correlation functionals. Unexpectedly good results were also obtained with G96P86/3-21G*, given each individual functionals performance in other functional pairings. MIDI! was outperformed, in general, by both 3-21G* and 3-21+G*.