Vibrational Spectrum of ‘3-iodo-2-propynenitrile (IC3N)’ from accurate CCSD(T)-F12b/MP2-F12 potential energy surface

The high-resolution infrared spectrum of IC 3 N has been the subject of numerous experimental studies. Relying on a hybrid anharmonic potential CCSD(T) -F12b/ MP2-F12 with cc-pVTZ-F12b basis sets and the application of a pure variational method (VCI), the IR spectrum of IC 3 N was calculated between 100 and 4600 cm −1 . These calculations allowed us to revisit the entire IR spectrum and assign a large part of its overtones, combinations bands with respect to experimental measurements. As it is shown in this work, the observed bands located at 1031 and 955 cm −1 could be explained in terms of Fermi resonance.