NEW TYPE OF SEMIEMPIRICAL MOLECULAR-ORBITAL METHOD FOR LARGE MOLECULES

A new type of molecular orbital method is proposed. It is applicable to large molecules containing large conjugated substructures. Only π-electrons in the conjugated part, but all-valence electrons in the non-conjugated part of a molecule, are taken into account explicitly. The Fock matrix elements are evaluated from the semi-empirical values employed in the existing all-valence-electron methods. The examples presented here suggest that the new type of MO method predicts electronic structures which are quite similar to those obtained by complete semi-empirical MO calculations. This new method may make it possible to reasonably well describe the electronic structure of, and interaction between, large molecules using considerably less computation time and core storage than the complete calculation analogs. © 1979.