Abstract: DFT-B3LYP was used to calculate the geometries of reactants, intermediates, transition states and products for NCS + NO reaction on the 6-31+G^* level. The transition states and intermediates of the reaction were verified by frequency analysis. The intrinsic reaction coordinate(IRC) calculations at the same level were also carried out to check the connection between all the critical structures located on the potential energy surface. Single point energies were calculated on the CCSD(T)/6-311+G^* level. The energy barriers, rate constants and thermodynamic quantities of the reaction were also calculated. The results show that the reaction system of the title reaction involves four paths, producing OCS+N₂(1), CS+N₂O(2), NS+OCN(3) and ONCNS(4) products, respectively. The NCS+NOOCS+N₂ is the dominant reaction path.

Key words: NCS radical, NO, Reaction mechanism, Kinetics