Ab Initio Anharmonic Analysis of Vibrational Spectra of Uracil Using the Numerical-Analytic Implementation of Operator Van Vleck Perturbation Theory

Krasnoshchekov, S.V.; Vogt, N.; Stepanov, N.F.

Авторы: Krasnoshchekov Sergey V., Vogt Natalja, Stepanov Nikolay F.
Журнал: The Journal of Physical Chemistry A: Molecules, Clusters, and Aerosols
Том: 119
Номер: 25
Год издания: 2015
Издательство: American Chemical Society
Местоположение издательства: United States
Первая страница: 6723
Последняя страница: 6737
DOI: 10.1021/acs.jpca.5b03241
Аннотация: 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 ∼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.
Добавил в систему: Краснощеков Сергей Вадимович

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Ab Initio Anharmonic Analysis of Vibrational Spectra of Uracil Using the Numerical-Analytic Implementation of Operator Van Vleck Perturbation Theoryстатья

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