Calculation of molecular vibrations: Selective scaling factors for semiempirical force constants
✍ Scribed by Grunenberg, J.; Herges, R.
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 238 KB
- Volume
- 18
- Category
- Article
- ISSN
- 0192-8651
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✦ Synopsis
The complete force constant matrices of a set of 50 aliphatic and aromatic hydrocarbons are calculated at the density functional theory Ž . B3LYPr6᎐31 q G d, p and semiempirical PM3 levels of theory. After transformation from Cartesian to nonredundant internal coordinates, the errors in the semiempirical force constants are systematically analyzed. The force constants of the C-C stretching coordinates can be easily corrected by a second-order fit. Thus, only two parameters are needed to reduce the mean error from 21.2 to 1.23%. The errors of other internal coordinates, particulary those including torsional modes, exhibit a larger diversity. The performance of the correction scheme in predicting vibrational spectra is shown for several examples Ž .