The role of kinetic energy in chemical binding

Research paper by William A. Goddard, C. Woodrow Wilson

Indexed on: 01 Sep '72Published on: 01 Sep '72Published in: Theoretical Chemistry Accounts


In a preceding paper, we examined the GI wavefunctions of small molecules and found that the nonclassical or exchange kinetic energy, Tx, dominates the changes in energy involved in chemical binding. Here we examine more closely the changes in Tx with internuclear separation and find that ΔTx is large for valence orbitals centered on different atoms because of the large region in which the orbitals are contragradient (i.e., have gradients in obtuse directions). In fact for H2 this contragradience accounts for 93% of the calculated binding energy. In addition, the behavior of Tx and ΔTx can usually be predicted from consideration of the permutational symmetry (Young tableau) involved in the wavefunction. The concepts developed here provide an alternative interpretation of the nature of the chemical bond.