Ionization of ammonium dinitramide: decomposition pathways and ionization products

The decomposition pathways of ionized ammonium dinitramide (ADN) have been analyzed using the B3LYP and the M06-2X density functional theory methods, coupled cluster theory and the composite CBS-QB3 method. Ionization and subsequent decomposition of the major decomposition products have also been studied. The ADN + ion dissociates into the stable DN radical and NH 4 + with a dissociation enthalpy of 50 kJ/mol. The subsequently formed DN + ion has an activation enthalpy of 102 kJ/mol for decomposition into N 2 O, O 2 and NO + . A competing pathway for ionization and decomposition of ADN involves the HDN + ion, which dissociates into NO 2 + and HNNO 2 with a barrier of only 17 kJ/mol. The ionization product HNNO 2 + is stable toward further decomposition, and the barrier for isomerization to HONNO + is 167 kJ/mol. The computed adibatic ionization potentials of ADN, HDN, DN and HNNO 2 are 9.4, 11.5, 10.2 and 10.9 eV, respectively. The results of the study have implications for the future use of ADN in propellants for electromagnetic space propulsion.