Indice de liaison en méthode CNDO. Relation entre indice de liaison et distance de liaison

The use of p_AB = Σ_μ^A Σ_ν^B _μν S_μν as bond index in the CNDO approximation is theoretically justified as it is an elaborated form of Coulson's bond order and an approximation of Roby's shared electron density. This bond index correlates with diatomic energy E_AB, a measure of binding energy, and with interatomic distance R_AB, for several bonds involving hydrogen and atoms of the n = 2 period. As an example of utilization of p_AB bond lengths in butadiene and a series of ethylenic compounds are determined.