VIBRATIONAL FREQUENCIES OF SIMPLE SULFUR-OXIDES - ABINITIO SQM AND MCSCF CALCULATIONS - COMPARISON

The values of the force constants and the vibrational frequencies of SO2 and SO3 have been computed through the scaled quantum mechanical (SQM) method and the multiconfigurational self consistent field (MCSCF) procedure. In the SQM procedure, we have tested the good transfer of the scale factors from SO2 to SO3 for the normal modes which are equivalent in both molecules (i.e. all the modes, except the A2" out-of-plane bending, evidently). The results obtained by the two methods for the vibrational frequencies are quite close and in good agreement with observation (namely a precision better than 4% for SO3).