A practical and efficient method to calculate AIM localization and delocalization indices at post-HF levels of theory.

A practical and efficient method is proposed for calculating localization and delocalization indices at post-Hartree-Fock levels, and the method is tested at the CISD/6-311G++(2d, 2p) level for a large set of molecules. Our method, which utilizes wave functions written in the natural molecular orbital format and obtained with GAUSSIAN 94 or GAUSSIAN 98, convincingly extends the concepts established at the HF level.