L'utilisation d'orbitales localisées dans l'étude théorique des molécules. II. Les hydrocarbures insaturés

The systematical study of the localized orbitals and their properties has been extended to the unsaturated hydrocarbons. The six simplest alkenes have been studied and fairly good transferability of the bond orbitals and their associated matrix elements may be pointed out. The influence of the neighbourhoods as well as the relative orientation of the bonds is discussed. These results lead to the use of a simple parametric procedure expressing the molecular orbitals as a combination of bond orbitals (LCLO-SCF-MO). This procedure is applied to saturated and unsaturated hydrocarbons, even conjugated hydrocarbons may be treated. Some original applications show that the results obtained by our procedure are comparable with the full ab initio calculations.