Population analysis based on occupation numbers II. Relationship between shared electron numbers and bond energies and characterization of hypervalent contributions

The population analysis based on occupation numbers, originally proposed by Davidson, is briefly reviewed. A new way is proposed to determine modified AOs and to characterize hypervalent contributions. This is discussed in application to the molecules NSF, NSF3, SF6, OPCl, OPCl2, O2PCl, SO2, ClO4−. It is the main objective of this work to investigate the connection between shared electron numbers σ — considered as a measure of covalent bond strength — and bond energies, σ is found to be a reliable measure of bond energies.