On the performance of density functional methods for describing atomic populations, dipole moments and infrared intensities

Atomic populations according to the Mulliken, electrostatic, natural population, and atomic polar tensor (APT) definitions were evaluated for first- and second-row compounds using different correlated ab initio techniques, DFP methods, and basis sets. All definitions except Mulliken exhibit modest basis set sensitivity. B3LYP predicts partial charges in agreement with high-level ab initio results. Exact-exchange corrections are more important than gradient corrections for this property. B3LYP with at least sdpf basis sets usually predicts dipole moments and infrared intensities in agreement with more accurate calculations, while semiquantitative IR intensities are obtained even with the modest cc-pVDZ basis set.