Comparison of ab initio Hartree-Fock and Kohn-Sham orbitals in the calculation of atomic charge, bond index, and valence

Atomic charges, bond indices (two-center and three-center), and valences have been calculated for a number of closed-shell molecules using ab initio Hartree-Fock (HF) and Kohn-Sham (KS) orbitals. In a few molecules we have also studied the variation of molecular valence, orbital energy and orbital valence with bond angle. Several basis sets and population analysis schemes have been employed in the present calculations. It is observed that, compared to the HF orbitals, the KS orbitals predict a slightly enhanced covalency. Otherwise, at least on the basis of bond index and related concepts, no appreciable difference is noticed between their performance in the theoretical study of bonding.