Initial Decomposition Mechanism of NH₃OH⁺N₅^– Crystal under Thermal and Shock Loading: A First-Principles Study

Abstract

NH 3 OH + N 5 − is a novel energetic material (EM) which has attracted much interest for its promising performances, including high energy density, high density, low sensitivity, and low toxicity. In this study, the initial decomposition mechanism of NH 3 OH + N 5 − crystal was investigated under thermal and shock loading by molecular dynamics simulation. First, programmed heating and constant temperature simulations were carried out by molecular dynamics simulation on the basis of density functional theory (DFT-MD). Results indicated that the initial decomposition reactions of NH 3 OH + N 5 − could be described by three reactions: proton transfer, ring-opening reaction, and cation decomposition and recombination, and three pathways of ring-opening reaction were found, including the ringopening of N 5 − , HN 5 , and H 2 N 6 . The first two reactions are the main pathways that produce N 2 molecules. Furthermore, we carried out DFT-MD simulations to study the shock decomposition behaviors of NH 3 OH + N 5 − , and three initial steps were proposed: N 5 − , HN 5 , and N 6 ring-opening. The fewer N 5 − and HN 5 ring-opening reactions were found during the shock simulation, accompanied by a significant change in the N 5 − bond angle. What's more, the transition states of decomposition reactions were investigated through quantum chemical calculations. The results revealed that the proton transfer reaction exhibits lower activation barriers compared to ring-opening reactions, and proton transfer would accelerate ring-opening reactions. In addition, the ring-opening reaction is the main energy-releasing reaction in the early stages of the decomposition. This work could promote the comprehension of the decomposition mechanism and energy release regularity of N 5 − ions.Article pubs.acs.org/JPCA