Research of the anharmonic effect on the main reactions related to NH3, NH2, and NH

NH₃ is a highly promising zero-carbon fuel. In this paper, 19 important reactions involving NH₃, NH₂, and NH in the ammonia system are studied to better establish the combustion reaction mechanism of ammonia. These reactions encompass the reactions of NH₃, NH₂, and NH with free radicals and inorganic compounds such as O, H, OH, NO, H₂O, and O₂. Utilizing the transition state theory and Yao-Lin method, energy barrier diagrams for these reactions are presented, and the harmonic and anharmonic rate constants are calculated over the temperature range from 300 to 4000 K. The calculation results reveal that, in most reactions, the harmonic rate constants exceed the anharmonic rate constants and the experimental results are closer to the anharmonic rate constants. Additionally, the kinetic and thermodynamic parameters are fitted. To summarize, most reactions are significantly influenced by the anharmonic effect.