Vibrational intensities and bond moments

Abstract

The determination of electrostatic bond moments from vibrational band intensities requires the calculation of the correction terms associated with the changes, occuring during vibration, of the molecular electronic wave function. A previously-defined correction scheme is discussed and is shown to be appropriate only to molecular orbital calculations employing an orthogonal basis set (as in CNDO/2); with a non-orthogonal basis the calculated corrections depend upon the origin chosen for the molecular coordinates, i.e. they are not translationally invariant. It is shown that translational invariance is restored when account is taken of the effect, on electron distribution, of the changes in overlap integrals which occur in molecular vibration.