Harmonic vibrational frequencies of several small organic molecules which were used to validate the scaled quantum mechanical (SQM) force field procedure of Pulay et al. were calculated using six popular density functional (DFT) methods and compared with experimental results. The combination of Becke's exchange with either Lee-Yang-Parr (BLYP) or Perdew's correlation functional (BP86) reproduces the observed frequencies satisfactorily with deviations similar to those of the Hartree-Fock SQM methods. Three hybrid DFT methods are found to yield frequencies which were generally higher than the observed fundamental frequencies. When the calculated frequencies were compared with 'experimental' harmonic frequencies however, Becke's three-parameter hybrid method with Lee-Yang-Parr correlation functional is found to be slightly more accurate, especially for C-H stretching modes. The results indicate that BLYP calculation is a very promising approach for understanding the observed spectral features.
| Identifer | oai:union.ndltd.org:ETSU/oai:dc.etsu.edu:etsu-works-14795 |
| Date | 01 January 1996 |
| Creators | Zhou, Xuefeng, Wheeless, Christine J.M., Liu, Ruifeng |
| Publisher | Digital Commons @ East Tennessee State University |
| Source Sets | East Tennessee State University |
| Detected Language | English |
| Type | text |
| Source | ETSU Faculty Works |
Page generated in 0.0018 seconds