SYMMETRIZED QUANTUM-MECHANICAL FORCE-FIELDS AND INS SPECTRA - S-TRIAZINE, TRICHLORO-S-TRIAZINE AND PYRAZINE

A vibrational analysis of the Inelastic Neutron Scattering (INS) spect ra of s-triazine, trichloro-s-triazina and pyrazine has been carried o ut starting from different ab initio calculations levels (HF/3-21G, HF /6-31G and MP2/6-31G*). Resulting force fields were transformed to th e symmetry-coordinate system and refined to the observed INS spectral profile. Similar final force fields result regardless of the level of the ab initio calculation. The importance of INS intensities in determ ining the values for the interaction constants is demonstrated.