Decomposition Pathways of Ammonium Dinitramide (ADN) and its HNO₃‐Clusters Elucidated by DFT‐Calculations

Abstract

Ammonium dinitramide (ADN) may serve as a ‘green’ oxidizer for rocket propellants since it provides chlorine free and minimum signature exhaust gases. However, stability issues and an erratic decomposition behaviour limit its non‐questionable general usability. Nitric acid (HNO3) is a decomposition product of ADN and is known to accelerate the decomposition autocatalytically. In this study, we investigate the effect of HNO3 on the initial decomposition steps of ADN via quantum chemical calculations based on density functional theory (DFT) in vacuo as well as in an aqueous solution. We establish and compare the reaction profiles of ADN, its anion DN− and its acid HDN as well as their HNO3‐clusters [NO3H_ADN], [NO3H_DN]− and [NO3H_HDN] towards the products NO2, HNO3 and N2O. All species exhibit various isomers with distinct decomposition pathways. We complement our study by investigating the protonated, cationic species [H_ADN]+, which may form in a low pH regime. The HNO3 clusters reveal modulated energy barriers and in part altered decomposition pathways in comparison to the free DN−, HDN, and ADN species. The altered pathways include the formation of reactive intermediates (such as H2NO3+) as well as the formation of two HNO3 molecules starting from one HNO3 molecule, hinting at accelerated decomposition of ADN due to interaction with HNO3.

ADN Solid Propellants with High Burning Rates as Booster Material for Hypersonic Applications

“…This leads to the assumption, that ADN decomposes near the surface and forms condensed species, e. g. nitric acid and its clusters and ammonium nitrate, like Lang and Bohn reported for the decomposition of pure ammonium dinitramide [27]. However, the detailed decomposition pathway for an ADN propellant is not fully investigated yet.…”

Detailed Kinetic Model for the Thermal Decomposition of Hydrazine Nitrate in Nitric Acid Solution Based on Quantum Chemistry Calculations Combined with the Polarizable Continuum Model

“…Green and co-workers investigated and established the mechanism for the reactions in the gas phase using transition state theory-based theoretical kinetics. Lang and Bohn found that the formation of the reactive H 2 NO 3 + can accelerate the decomposition of ammonium dinitramide (NH 4 N­(NO 2 ) 2 ) based on the DFT calculations. These reactions may play an important role in HN decomposition, but this is the subject of future study.…”