title: Covalent bonds are created by the drive of electron waves to lower their kinetic energy through expansion.
abstract: An analysis based on the variation principle shows that in the molecules H2 (+), H2, B2, C2, N2, O2, F2, covalent bonding is driven by the attenuation of the kinetic energy that results from the delocalization of the electronic wave function. For molecular geometries around the equilibrium distance, two features of the wave function contribute to this delocalization: (i) Superposition of atomic orbitals extends the electronic wave function from one atom to two or more atoms; (ii) intra-atomic contraction of the atomic orbitals further increases the inter-atomic delocalization. The inter-atomic kinetic energy lowering that (perhaps counter-intuitively) is a consequence of the intra-atomic contractions drives these contractions (which per se would increase the energy). Since the contractions necessarily encompass both, the intra-atomic kinetic and potential energy changes (which add to a positive total), the fact that the intra-atomic potential energy change renders the total potential binding energy negative does not alter the fact that it is the kinetic delocalization energy that drives the bond formation.
authors.affiliation: Department of Chemistry and Ames Laboratory USDOE, Iowa State University, Ames, Iowa 50011, USA.
authors.forename: Michael W
authors.initials: MW
authors.lastname: Schmidt
authors.affiliation: Advanced Biomedical Computing Center, Information Systems Program, Leidos Biomedical Research, Inc., Frederick National Laboratory for Cancer Research, Frederick, Maryland 21702, USA.
authors.forename: Joseph
authors.initials: J
authors.lastname: Ivanic
authors.affiliation: Department of Chemistry and Ames Laboratory USDOE, Iowa State University, Ames, Iowa 50011, USA.
authors.forename: Klaus
authors.initials: K
authors.lastname: Ruedenberg
mesh_terms: D004583:Electrons; D006859:Hydrogen / Q000737:chemistry*; D006860:Hydrogen Bonding; D007700:Kinetics; D055585:Physical Phenomena; D011789:Quantum Theory; D013816:Thermodynamics
chemical_list: D006859:Hydrogen