First principles based microkinetic simulations of ammonium dinitramide decomposition on Cu(111)

Ammonium dinitramide (ADN), a highly promising new oxidizer, is poised to potentially replace ammonium perchlorate (NH4ClO4) in rocket propellants due to its superior energy density and reduced combustion pollution. This study utilizes density functional theory (DFT) to delve into the thermal decomposition mechanism of ADN on a copper substrate and its reaction mechanism in the gas phase. Given the diversity and complexity of ADN's thermal decomposition and combustion processes, the focus here is on one specific decomposition pathway. Initially, ADN decomposes into ammonia (NH3) and dinitramide (HDN), which then undergoes further breakdown. Various isomers of HDN, such as HON(O)NNO2 or HN(NO2)2, are considered. For HON(O)NNO2, the preferred decomposition route appears to form nitric acid (HNO3) and nitrous oxide (N2O). The calculations suggest that under the catalytic influence of copper, ADN decomposes more rapidly. Furthermore, this study explores how temperature affects reaction kinetics, finding that as the reaction temperature increases, so do the production rates of ADN decomposition products including HNO3, NH3, N2O, H2, and N2. In conclusion, analyses of charge density differences and Bader charges of ADN, HDN, and NH3 on the copper surface reveal a clear electron transfer from the copper to the hydrogen and nitrogen atoms, enhancing our understanding of the reaction kinetics.