Calculations of vibrational energy levels by using a hybrid ab initio and DFT quartic force field: application to acetonitrile.
A hybrid quartic force field with quadratic force constants calculated at the CCSD(T)/cc-pVTZ level and cubic and quartic terms determined by a B3LYP/cc-pVTZ treatment is proposed to compute the vibrational energy levels of acetonitrile from a variational method. Fundamentals and overtones calculated in the range of 300-3200 cm(-1) are in fair agreement with the 31 observed data, with an absolute mean deviation of less than 0.8%. These results allow us to explain several Fermi resonances.
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Laboratoire de Chimie Théorique et Physico-Chimie Moléculaire - UMR 5624, Fédération de Recherche IPREM 2606, Université de Pau et des Pays de l'Adour, IFR - Rue Jules Ferry, 64000 PAU, France. didier.begue@univ-pau.fr
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Pouchan
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