On the future of the Huckel model

In an attempt to foresee the prospects of the qualitative trend in quantum chemistry, the place of the Huckel model is analyzed in the broad context of quantum mechanical and chemical perspectives on the molecular world. Quantum mechanics and chemistry are considered as complementary approaches to molecular structure and properties that are irreducible one to another. Arguments are given for the hypothesis that the Huckel model makes a separate level of investigation of molecules situated in between quantum mechanics and chemistry. In this context, the need is emphasized for development of new concepts immanent in the very Huckel model. These concepts are anticipated to play the role of terms for qualitative orbital thinking, the persistent need for which was emphasized recently (R. Hoffmann, J. Mol. Struct. (Theochem), 424 (1998) 1). (C) 1999 Elsevier Science B.V. All rights reserved.