DFT and HF–DFT calculations of 14N quadrupole coupling constants in molecules Original Research Article

The efficacy of several DFT and HF–DFT methods for the calculation of 14N quadrupole coupling constants in molecules has been investigated. Valence triple-zeta quality Pople and Dunning correlation consistent type bases were used. Assessment of the different methods was made by linear regression analysis of the calculated efgʹs versus the experimental nqccʹs. The HF–DFT methods were found superior to the DFT methods. The least residual standard deviation was obtained with the B3PW91/6-311+G(df,pd) model. For 39 molecules containing 45 nitrogen sites, the standard deviation is 30 kHz (1.3%). Regarding the Dunning type aug-cc-pVTZ basis, it was found that the addition to nitrogen of core–valence correlation functions significantly improves the results.