Computational and Spectroscopic Studies of Carbon Disulfide

The vibrational spectroscopy of CS₂ has been investigated many times in all three phases. However, there is still some ambiguity about the location of two of the modes in the solid state. The aim of this work was to locate all of the modes by inelastic neutron scattering (INS) spectroscopy, (which has no selection rules), and to use periodic density functional theory to provide a complete and unambiguous assignment of all the modes in the solid state. A comparison of the observed and calculated INS spectra shows generally good agreement. All four of the ν₂ bending mode components are calculated to fall within 14 cm^-1. Inspection of the spectrum shows that there are no bands close to the intense feature at 390 cm^-1 (assigned to ν₂); this very strongly indicates that the A mode is within the envelope of the 390 cm^-1 band. Based on a simulation of the band shape of the 390 cm^-1 feature, the most likely position of the optically forbidden component of the ν₂ bending mode is 393 ± 2 cm^-1. The calculations show that the optically inactive A translational mode is strongly dispersed, so it does not result in a single feature in the INS spectrum.