A comparative coupled cluster and density functional theory study of the HOCI → HCIO transition state

Abstract

The structural features of the HOCl → HClO isomerization mechanism, including all stationary points, and one saddle point, were examined by use of coupled cluster and the B3LYP density functional theory methodology. To improve the results a very large 6–311++G (3df, 3pd) Gaussian-type basis set was employed in the presented calculations. In addition, Gaussian-3 theory was tested against our coupled cluster (with single, double and triple excitations) results, and they were found to correlate closely with one another by around 1–2 kcal mol⁻¹. The energy change for this isomerization reaction is predicted to be 54.5 kcalmol⁻¹ and 52.5 kcalmol⁻¹ with the B3LYP and CCSD (T) methods, respectively, and the activation barrier is 76.1 kcal mol⁻¹ and 70.1 kcalmol⁻¹ with the same methods.