ON THE PERFORMANCE OF DENSITY-FUNCTIONAL METHODS FOR DESCRIBING ATOMIC POPULATIONS, DIPOLE-MOMENTS AND INFRARED INTENSITIES

Atomic populations according to the Mulliken, electrostatic, natural p opulation, and atomic polar tensor (APT) definitions were evaluated fo r first- and second-row compounds using different correlated ab initio techniques, DFP methods, and basis sets. All definitions except Mulli ken exhibit modest basis set sensitivity. B3LYP predicts partial charg es in agreement with high-level ab initio results. Exact-exchange corr ections 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 mode st cc-pVDZ basis set.