Abstract: A doublet potential energy surface for the reaction of HCCN radical with molecular NO is worked out at the CCSD(T)/6-311G(d,p)//B3LYP/6-311G(d,p) +ZPE level to give four products: P1(HCN+NCO), P2(OH+NCCN), P₃[HCN+(CNO)] and P4(HCN+CNO). It is shown that product P1 is the major one, product P2 is the minor one, and products P₃ and P4 are hard to be obtained. For the pathways to the major product P1 and the minor product P2, the single point energies are also calculated at the G2(B3LYP/MP2/CC) level of theory for precision. On the other hand, the quartet potential energy surface for the reaction is also considered, but there is no favorable pathway in it.

Key words: Cyanomethylene radical, Nitrogen oxide, Ab initio method, Reaction potential energy surface