SEMI-EMPIRICAL ALL VALENCE ELECTRONS SCF-MO-CNDO THEORY .4. DIPOLE MOMENTS

The calculation of molecular dipole moments in the SCF-MO-CNDO theory is considered. The question of translational invariance is examined, and it is shown that the formula for dipole moments used in MO theories including overlap cannot be used in the CNDO approximation. The Pople-Segal formula for dipole moments is shown to be the most accurate of several approximate formulae with the required invariance property. For molecules containing only hydrogen and first-row atoms, the semi-empirical SCF-MO-CNDO theory predicts dipole moments about as accurately as the Pople-Segal CNDO/2 theory, and much more accurately than the Extended Hückel Theory. For molecules containing heavier atoms, the semiempirical theory fails. © 1968 Springer-Verlag.