Energy partitioning for generalized product functions: The interference contribution to the energy of generalized valence bond and spin coupled wave functions

The main driving force for the formation of the covalent bond is the quantum-mechanical interference effect among one-electron states, as has been suggested in several works by the use of partition schemes to calculate the interference contributions to the energy. However, due to some difficulties associated with the original approaches, calculations were only carried out for a few, mostly diatomic molecules. In this work, we propose a general approach of partitioning based on generalized product functions with generalized valence bond at the perfect pairing approximation and spin-coupled groups, which should allow the investigation of a broader array of molecules, and hopefully, shed light on the nature of the chemical bond in molecules with unusual chemical features. Among other things, this approach lends itself naturally to the investigation of interference in individual bonds or groups of bonds in a molecule.