Article révisé par les pairs
Résumé : This work describes an improved semi-empirical Hückel-method for the study of physicochemical properties of aromatic systems. Coherent heteroatomic coulomb- and exchange parameters are calculated according to McWeeny's theory [30]. The variation of the exchange integrals βijwith bond length is introduced in the calculations by means of an iterative "selfconsistent β"-procedure. A new iteration function for the aromatic C=C link and a general method to obtain similar relations for several heteroatomic bonds are described. A simple computer program calculating various molecular properties is presented. © 1967 Springer-Verlag.