Correlating Chemical Bonding With the Potential Energy Acting on One Electron in a Molecule

The potential energy acting on one electron in a molecule (PAEM) (i.e., the energy associated with the interactions of one local electron with all nuclei and remaining electrons) is defined and calculated using an ab initio method, and exhibits interesting spatial characteristics. A chemical bond path or bond line (bond bar or stick) is defined or described by a local minimum PAEM line in the vicinity of the path between two adjacent atoms. The strength of a bond is intimately related to the features of the bond center (bc), which corresponds to the PAEM saddle point around the bond path. The PAEM at the bond center along the chemical bond correlates quantitatively with bond length and binding energy. A PAEM-MO diagram is introduced, which clearly distinguishes chemical bonding from nonbonded and/or van der Waals interactions. Furthermore, the electron interflow frequency (EIF) along the bond path at the bc can be defined from the PAEM around the bc; the EIF correlates with the bond-vibration frequency. The properties of the bc along the bond path and the saddle point along the intrinsic reaction coordinate on the potential energy surface are related in a very interesting manner.