Multireference configuration interaction singles and doubles (MR-CISD) and multireference averaged quadratic coupled clusters (MR-AQCC) were used to study geometry optimization and adiabatic excitation energies of the lowest four valence states of formaldehydes. The harmonic vibrational frequencies and infrared (IR) intensities for the ground states were collected and compared with other theoretical and experimental harmonic frequencies. The results showed that the bond distance and the bond angle determined the planar geometry at the crossing seam and the occurrence of the conical intersections made the ultraviolet (UV) spectrum very irregular.
|Number of pages||12|
|Journal||Journal of Chemical Physics|
|State||Published - 2001|