Structure, harmonic vibrational frequencies, and dipole moment derivatives of methane, ethylene, and acetylene have been obtained from generalized valence bond (GVB) wave function calculations. The results are compared to Hartree-Fock (HF) data, and other correlated wave function data. It is found that the GVB method consistently overemphasizes left-right electron correlation effects, and predicts bond lengths ∼0.01-0.02 Å longer than experiment. However, the calculated harmonic frequencies are within 4.2% of the observed fundamentals and within 3.5% of the experimental harmonic frequencies. Dipole moment derivatives are in semi-quantitative agreement with experiment. The method is used to predict the IR spectrum of the vinyl radical, including a very intense out of plane bending mode with frequency near 1000 cm-1.
ASJC Scopus subject areas
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry