TITLE

Fermi resonance in CO2: A combined electronic coupled-cluster and vibrational configuration-interaction prediction

AUTHOR(S)
Rodriguez-Garcia, Valerie; Hirata, So; Yagi, Kiyoshi; Hirao, Kimihiko; Taketsugu, Tetsuya; Schweigert, Igor; Tasumi, Mitsuo
PUB. DATE
March 2007
SOURCE
Journal of Chemical Physics;3/28/2007, Vol. 126 Issue 12, p124303
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
The authors present a first-principles prediction of the energies of the eight lowest-lying anharmonic vibrational states of CO2, including the fundamental symmetric stretching mode and the first overtone of the fundamental bending mode, which undergo a strong coupling known as Fermi resonance. They employ coupled-cluster singles, doubles, and (perturbative) triples [CCSD(T) and CCSDT] in conjunction with a range of Gaussian basis sets (up to cc-pV5Z, aug-cc-pVQZ, and aug-cc-pCVTZ) to calculate the potential energy surfaces (PESs) of the molecule, with the errors arising from the finite basis-set sizes eliminated by extrapolation. The resulting vibrational many-body problem is solved by the vibrational self-consistent-field and vibrational configuration-interaction (VCI) methods with the PESs represented by a fourth-order Taylor expansion or by numerical values on a Gauss-Hermite quadrature grid. With the VCI, the best theoretical estimates of the anharmonic energy levels agree excellently with experimental values within 3.5 cm-1 (the mean absolute deviation). The theoretical (experimental) anharmonic frequencies of the Fermi doublet are 1288.9 (1285.4) and 1389.3 (1388.2) cm-1.
ACCESSION #
24601933

 

Related Articles

Share

Read the Article

Courtesy of THE LIBRARY OF VIRGINIA

Sorry, but this item is not currently available from your library.

Try another library?
Sign out of this library

Other Topics