TY - JOUR
T1 - Fermi resonance in CO2
T2 - A combined electronic coupled-cluster and vibrational configuration-interaction prediction
AU - Rodriguez-Garcia, Valerie
AU - Hirata, So
AU - Yagi, Kiyoshi
AU - Hirao, Kimihiko
AU - Taketsugu, Tetsuya
AU - Schweigert, Igor
AU - Tasumi, Mitsuo
N1 - Funding Information:
The authors affiliated with the University of Florida are thankful for the financial support from the University of Florida Division of Sponsored Research and the U.S. Department of Energy (Grant No. DE-FG02-04ER15621).
PY - 2007
Y1 - 2007
N2 - 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.
AB - 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.
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U2 - 10.1063/1.2710256
DO - 10.1063/1.2710256
M3 - Article
C2 - 17411119
AN - SCOPUS:34047165939
SN - 0021-9606
VL - 126
JO - Journal of Chemical Physics
JF - Journal of Chemical Physics
IS - 12
M1 - 124303
ER -