ž / VBDFT s : a Huckel - type semi - empirical valence bond method ̈ scaled to density functional energies . Application to linear polyenes

Ž . Ž . A semi-empirical valence bond VB method, called VBDFT s , is described and applied to C H conjugated n nq2 hydrocarbons. The method is a Huckel-type VB scheme with energies scaled to density functional theory energies based on a ̈ single parameter; the matrix element l due to spin transposition between bonded atoms. Total energies, excitation energies, resonance and p-bond energies are presented for the various species. The insight that can be derived from the corresponding wavefunctions is discussed. q 1998 Elsevier Science B.V. All rights reserved.