Coupled calculations of vibrational frequencies and intensities. VIII. Raman and infrared activity measure of normal vibrations of non-chiral and chiral molecules and molecular crystals

Abstract

Making use of the transformation properties of the Cartesian eigenvectors simple procedures are described which calculate ‘activity measures’ (AM) for normal vibrations, showing the symmetry species of the vibrations through the non-vanishing components of the tensor of the molecular polarizability change and the vector of the dipole moment change. They can be applied to molecules of any size and they do not need adjustable parameters. They are appropriate for molecules which are too large for proper application of the coupled calculation of intensities (ref. 1–6) on the base of the CNDO-procedure. Similar procedures are described to calculate the chiral activity measured for chiral molecules and the activity measures for molecular crystals. The AM procedures are useful for the assignment of calculated to observed vibrations, for the refinement of force fields and the estimation of molecular structures.