The Binding Energy of the σ Bond, III. Discussion on the Ionic Structures

Abstract

The ionic terms of the σ bonds are explicitly considered by the use of the semi-localized orbitals and their contribution to the binding energy of the bond is discussed. A theoretical basis for the relation between Pauling's scale of electronegativity and Mulliken's one is given under some assumptions. The value of the binding energy of the C-C bond in the diamond crystal is computed to be 3.64 eV per bond, if the ionic terms of the bond are included. It is shown that the value of the binding energy of the diamond crystal in the Heitler-London approximation is almost equal to that in the molecular orbital method and less than the above value by about 0.4 eV per bond. The resultant state, however, is found to be rather well expressed by the Heitler-London approximation.