Performance assessment of density functional theory-based models using orbital momentum distributions

Abstract

The performance of a number of established and widely used density functional theory (DFT) methods (B3LYP, Bhandh, BP86, PW91, Vosko, Wilk, and Nusair (VWN), LB94, PBe0, statistical average of orbital potentials (SAOP) and X3LYP) and the Hartree–Fock (HF) method has been assessed using the 7σ orbital momentum distributions (MDs) of nitrous oxide (N2O). The DFT methods are combined with a number of Gaussian basis sets as well as even-tempered Slater basis sets. Orbital MDs of N2O are compared with experimental measurement of the same orbital from electron momentum spectroscopy. This study reveals information regarding the performance of (a) the DFT methods and their long-range behaviour, (b) Gaussian and Slater basis set contributions to this orbital, (c) combinations (i.e. the models) of the DFT methods and basis sets and (d) the entire region of chemical significance of the orbital. In general, for any given method, it is found that Slater basis sets achieve better overall agreement with experiment than Gaussian basis sets. Dunning's aug-cc-pVTZ basis set achieves the best performance for the MDs for this orbital among the Gaussian basis sets. The B3LYP and BP86 models exhibit similar overall performance to more recent models such as X3LYP and SAOP. This study also demonstrates that the particular combination of density functional method and basis set employed have a significant effect on the quality of the calculated orbitals.