Schmidt Michael W, Ivanic Joseph, Ruedenberg Klaus
Department of Chemistry and Ames Laboratory USDOE, Iowa State University, Ames, Iowa 50011, USA.
Advanced Biomedical Computing Center, Information Systems Program, Leidos Biomedical Research, Inc., Frederick National Laboratory for Cancer Research, Frederick, Maryland 21702, USA.
J Chem Phys. 2014 May 28;140(20):204104. doi: 10.1063/1.4875735.
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.
基于变分原理的分析表明，在分子H2(+)、H2、B2、C2、N2、O2、F2中，共价键是由电子波函数离域化导致的动能衰减所驱动的。对于平衡距离附近的分子几何结构，波函数的两个特征有助于这种离域化：(i)原子轨道的叠加将电子波函数从一个原子扩展到两个或更多原子；(ii)原子轨道的原子内收缩进一步增加了原子间的离域化。原子内收缩（可能与直觉相反）导致的原子间动能降低驱动了这些收缩（收缩本身会增加能量）。由于收缩必然同时包含原子内动能和势能变化（两者相加为正的总和），原子内势能变化使总势能结合能为负这一事实并不会改变是动能离域化能量驱动键形成这一事实。
