期刊
JOURNAL OF PHYSICAL CHEMISTRY A
卷 119, 期 25, 页码 6723-6737出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.jpca.5b03241
关键词
-
资金
- Dr. B. Mez-Starck Foundation (Germany)
The numerical-analytic implementation of the Operator version of the canonical Van Vleck second-order Vibrational perturbation theory (CVPT2) is employed for a purely ab initio prediction and interpretation of the infrared (IR) and Raman anharmonic spectra of a medium-size molecule of the diketo tautomer of uracil (2,4(1H,3H)-pyrimidinedione), which has high biological importance as one of the four RNA nucleobases. A nonempirical, semidiagonal quartic potential energy surface (PES) expressed in normal coordinates was evaluated at the MP2/cc-pVTZ level of theory. The quality of the PES was improved by replacing the harmonic frequencies with the best estimated CCSD(T)-based values taken from the literature. The theoretical method is enhanced by an accurate treatment of multiple Fermi and Darling-Dennison resonances with evaluation of the corresponding resonance constants W and K (CVPT2+WK method). A prediction of the anharmonic frequencies as well as IR and Raman intensities was used for a detailed interpretation of the experimental spectra of uracil Very good agreement between predicted and observed vibrational frequencies has been achieved (RMSD similar to 4.5 cm(-1)). The model employed gave a theoretically robust treatment of the multiple resonances in the 1680-1790 cm(-1) region: Our new analysis gives the most reliable reassignments of IR and Raman spectra of uracil available to date.
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