Calculation of Vibrational Parameters of an Electride-Like Molecule Li4C4H2N2 and the Pyridazine Molecule C4H4N2

Abstract

The frequencies and intensities are calculated for fundamental transitions between vibrational states of an electride-like molecule Li₄C₄H₂N₂ that can be obtained from the pyridazine molecule C₄H₄N₂ by replacing two hydrogen atoms by lithium atoms and adding two other lithium atoms to nitrogen atoms. Spectral parameters of Li₄C₄H₂N₂ are calculated in the harmonic and anharmonic approximations using the MP2, CCSD, and QCISD methods with the sets of atomic functions aug-cc-pVDZ and aug-cc-pVTZ. For comparison the absorption spectrum of a pyridazine molecule was calculated in the same approximations. The calculations showed that, upon introducing lithium atoms into the pyridazine molecule, new intense bands appear and the spectral parameters of the bands present in the pyridazine spectrum are significantly changed. The results obtained may be useful for spectroscopic observation and identification of the new c-ompound.