Molecular Vibrations of Pyramidal C 3v Molecules: Application of the Keating Bendings

The Keating force field of pyramidal XY 3 molecules is defined in analogy with valence and central force fields. Its usefulness in comparison with valence and central force fields is discussed. Different "exact" force fields are also investigated and expressed in terms of valence, central and Keating coordinates. This approach indicates the superiority of the coordinate system which gives the smallest magnitude of the interaction force constant. The conclusions are not unequivocal, but they go in favour of the Keating coordinates when the most reliable calculations are considered.