CALCULATIONS OF MOLECULAR VIBRATIONAL FREQUENCIES USING SEMIEMPIRICAL METHODS

MINDO/3, MNDO, AM1, and PM3 calculations of molecular vibrational frequencies are reported for 61 molecules. All techniques were applied to both well-behaved and badly behaved systems. Overall, MINDO/3 and MNDO were found to contain rather large errors whereas AM1 and PM3 were relatively accurate. Since no technique does well for all molecules, the technique used should be chosen based on the molecular vibration of interest. In general, AM1 and PM3 together provide fairly accurate results.