Ab initio determination of the heat of formation of ketenyl (HCCO) and ethynyl (CCH) radicals

The heats of formation of ketenyl ( HCCO) and ethynyl ( CCH) radicals have been obtained from high level ab initio calculations. A set of reactions involving HCCO, CCH and species with well-known heats of formation has been considered. The reaction enthalpies have been calculated from the total energy of the species involved. These calculations include a non-relativistic electronic energy from extrapolated coupled-cluster calculations ( up to CCSDTQ), corrections for scalar relativistic and spin-orbit effects, as well as the diagonal Born-Oppenheimer correction. This study also presents an accurate equilibrium geometry for HCCO as well as harmonic and fundamental frequencies for both HCCO and CCH.