Molecular Orbital Method and Molecular Ionization Potentials

(1) Empirical evidence indicates that, other things being equal, the atomic integral α of the LCAO molecular orbital method decreases in magnitude, (a), with increasing interatomic distance, (b), with increase in the number of atoms covered by a MO.(2) Theoretical computations give a satisfactory account of effect (a), and (except for the absolute values of α in many-center cases) also of effect (b).(3) It is reasonable to hope that further study of theoretical approximation methods of the MO type will make possible an increasingly quantitative theoretical understanding of molecular ionization potentials and of other molecular properties.