# Explicitly Correlated Coupled Cluster Calculations for Propadienylidene (H_{2}CCC)

journal contribution

posted on 16.09.2010, 00:00 by Peter Botschwina, Rainer OswaldPropadienylidene (H

_{2}CCC), a reactive carbene of interest to combustion processes and astrochemistry, has been studied by explicitly correlated coupled cluster theory at the CCSD(T)-F12x (x = a, b) level. Vibrational configuration interaction (VCI) has been employed to calculate accurate wavenumbers for the fundamental vibrations of H_{2}CCC, D_{2}CCC, and HDCCC. The symmetric CH stretching vibration of H_{2}CCC is predicted to occur at ν_{1}= 2984 cm^{−1}. Absorptions observed by argon matrix infrared spectroscopy at 3049.5 and 3059.6 cm^{−1}are reassigned to the combination tone ν_{2}+ ν_{4}, which interacts with ν_{1}and is predicted to have a higher intensity than the latter. Furthermore, IR bands detected at 865.4 and 868.8 cm^{−1}are assigned to ν_{6}(HDCCC), and those observed at 904.0 and 909.8 cm^{−1}are assigned to the out-of-plane bending vibration ν_{8}(HDCCC). An accurate value of 79.8 ± 0.2 kJ mol^{−1}is recommended for the zero-point vibrational energy of H_{2}CCC.