Theoretical determination of the heat of formation of methylene

Abstract

The heat of formation of CH₂ has been calculated using high accuracy ab initio results for its dissociation energy. MRCI calculations were carried out with correlation consistent polarized valence basis sets (cc-p VXZ, X=2–6). Core-valence correlation energies were computed using CCSD(T) with correlation consistent polarized core–valence basis sets (cc-pCVXZ, X=2–5). For the ground state CH₂(X̃³B₁) our best estimate of the heat of formation at 0 K is Δ_f,0H^E=388.7±0.6 kJ mol^-1. This is in agreement with experimental results, in the range 384.5–395.8 kJ mol^-1. Our result implies that for the first excited state CH₂(ã¹A₁), Δ_f,0H^E=426.4±0.6 kJ mol^-1.

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