Accurate Determination of the Equilibrium and Vibrationally Averaged Structural and Molecular Properties of Difluoromethanimine (F2CNH) from ab Initio Calculations

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The availability of large core-valence basis sets together with highly accurate coupled-cluster calculations allow us to present an improved determination of the equilibrium structure of the difluoromethanimine molecule. Core correlation effects and basis set incompleteness have been taken into account to obtain best estimates of the equilibrium geometry. In addition, two important molecular properties, namely, the dipole moment and the nuclear quadrupole coupling constants, have been investigated. The molecular dipole moment has been calculated at the coupled-cluster level using basis sets of different quality, including diffuse functions and taking into account both core correlation effects and basis set incompleteness. The quadrupole coupling constants, evaluated from the electric field gradient at the quadrupolar nuclei, have been computed at the multiconfiguration self-consistent field, Moller-Plesset perturbation to second order, and coupled-cluster levels of theory employing large core-valence basis sets. Because experiment usually determines vibrational ground state molecular parameters, to directly compare theoretical and experimental results a vibrational averaging procedure has been carried out. This allowed us to evaluate the vibrational corrections both for the molecular structure and properties investigated.