Geometry optimization of excited valence states of formaldehyde using analytical multireference configuration interaction singles and doubles and multireference averaged quadratic coupled-cluster gradients, and the conical intersection formed by the 1 1B1(σ-π*) and 2 1A1(π-π*) states

Michal Dallos, Thomas Müller, Hans Lischka, Ron Shepard

Research output: Contribution to journalArticle

37 Scopus citations

Abstract

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.

Original languageEnglish
Pages (from-to)746-757
Number of pages12
JournalJournal of Chemical Physics
Volume114
Issue number2
DOIs
StatePublished - 2001

Fingerprint Dive into the research topics of 'Geometry optimization of excited valence states of formaldehyde using analytical multireference configuration interaction singles and doubles and multireference averaged quadratic coupled-cluster gradients, and the conical intersection formed by the 1 <sup>1</sup>B<sub>1</sub>(σ-π*) and 2 <sup>1</sup>A<sub>1</sub>(π-π*) states'. Together they form a unique fingerprint.

  • Cite this