The decomposition pathways of ammonium dinitramide on the basis of ab initio calculations

Quantum chemistry calculations incorporating solvent effects were used to investigate the decomposition pathways in molten Ammonium dinitramide (ADN). Optimized structures for reactants and products were obtained at the CBS-QB3//ωB97XD/6–311++G(d,p)/SCRF = (solvent = water) level of theory, considering the isomers ADNI (NH4–N(NO2)2) and ADNII (NH4–ON(O)NNO2) and the four ADNII conformers, which are minimal clusters of anion and cation in molten ADN. In the initial stage of decomposition, the ADNII decomposes to NO2∙ and NNO2NH4. Following the initial decomposition, NNO2NH4∙ decomposes to N2O, NH3, and OH∙, and the OH∙ combines NO2∙ to yield HNO3. This decomposition can be written using one global formula: ADN → N2O + NH4NO3 (NH3 + HNO3).