Theoretical study on the mechanism of the NH3 plus NO reaction on the doublet potential energy surfaces

Kinetic and mechanism of atmospheric reaction of ammonia (NH3) and nitric oxide (NO) on the doublet potentialenergy surfaces have been investigated in details using ab initio and DFT methods. All stationary points involved in thetitle reaction were optimized at the B3LYP and MP2 methods of computation in connection with the 6-311++G (d, p)and 6-311++G (3df, 3pd) basis set. For calculation of accurate energies, the CCSD(T) method is applied. Also,thermodynamic parameters and rate constant are calculated at B3LYP method with the mentioned basis set. The resultsshow that direct hydrogen abstraction mechanism is the most important pathways of reaction. Two pre-reactivecomplex, C1, was formed between ammonia and nitric oxide. Three different products are suggested which all of themhave enough thermodynamic stability. The production of NH2 + HON is the main reaction channel in thermodynamicviewpoint with standard Gibbs free energy of ΔG0 = -10.56 kcal/mol at B3LYP level. The rate constant is calculated atthe 300-2500 K temperature range for the reliable pathway of the mentioned at MP2/6-311++(d, p) method.

Keywords:

kinetic , mechanism , ammonia , rate constant , thermodynamic