Theoretical investigations of the IR spectroscopy of Ni(C2S2H2)2. A case study of the P_VMWCI2 algorithm including anharmonic effects

Abstract

The near infrared (NIR) spectra of bis(ethylene-1,2-dithiolato)nickel, Ni(C₂S₂H₂)₂ are fully interpreted here by applying a method developed for efficient automatic computation of both the infrared wave numbers and the intensities. The employed procedure uses parallel variational multiple window configuration interaction wave functions, the so-named P_VMWCI₂ algorithm, which incorporates both the mechanical and the electric anharmonic effects. It is shown that inclusion of anharmonicities is crucial for correctly assigning the fundamental, combination, and overtone vibrational frequencies in the infrared spectrum of the target system, for which conflicting assignments are found in literature.