Structural Dynamics of Chloromethanes through Computational Spectroscopy: Combining INS and DFT

In this work, the structural dynamics of the chloromethanes CCl₄, CHCl₃ and CH₂Cl₂ were evaluated through a computational spectroscopy approach by comparing experimental inelastic neutron scattering (INS) spectra with the corresponding simulated spectra obtained from periodic DFT calculations. The overall excellent agreement between experimental and calculated spectra allows a confident assignment of the vibrational features, including not only the molecular fundamental modes but also lattice and combination modes. In particular, an impressive overtone sequence for CHCl₃ is fully described by the simulated INS spectrum. In the CCl₄ spectrum, the splitting of the ν3 mode at ca. 765-790 cm^-1 is discussed on the basis of the Fermi resonance vs. crystal splitting controversy.