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 ha ve been calculated for a number of closed-shell molecules using ab initio H artree-Fock (HF) and Kohn-Sham (KS) orbitals. In a few molecules we have al so studied the variation of molecular valence, orbital energy and orbital v alence with bond angle. Several basis sets and population analysis schemes have been employed in the present calculations. It is observed that, compar ed to the HF orbitals, the KS orbitals predict a slightly enhanced covalenc y. Otherwise, at least on the basis of bond index and related concepts, no appreciable difference is noticed between their performance in the theoreti cal study of bonding.