ReaxFF-Based Molecular Dynamics Study of the Mechanism of the Reaction of N2O4 with H2O

Yi Guo; Gan Tian; Xinlong Chang; Zhanmei Tang; Zhiyong Huang; Dejun Liu; Xinzhi Yang

doi:10.1021/acsomega.3c08695

ReaxFF-Based Molecular Dynamics Study of the Mechanism of the Reaction of N₂O₄ with H₂O

ACS Omega. 2024 Apr 15;9(17):18893-18900. doi: 10.1021/acsomega.3c08695. eCollection 2024 Apr 30.

Authors

Yi Guo¹, Gan Tian¹, Xinlong Chang¹, Zhanmei Tang², Zhiyong Huang¹, Dejun Liu¹, Xinzhi Yang¹

Affiliations

¹ School of Missile Engineering, Rocket Force University of Engineering, Xi'an 710025, China.
² Beijing Institute of Aerospace Testing Technology, Beijing 100074, China.

Abstract

During long-term storage of the liquid propellant N₂O₄, it absorbs H₂O to form the N₂O₄(H₂O)_n system, and this in turn generates HNO₃, HNO₂, and other substances in the storage tank because of corrosion, which seriously affects the performance of weaponry. In this work, we carried out computational simulations of N₂O₄ with different masses of water based on ReaxFF, analyzed the reaction intermediates and products, and investigated the mechanism of the reaction of N₂O₄ with H₂O and of N₂O₄(H₂O)_n. The results show that the reaction product ω(HNO₃+HNO₂) undergoes a rapid growth in the early stage of the reaction and then tends toward dynamic equilibrium; the potential energy of the system decreases with the increase of ω(H₂O), the reaction rate increases, and the rate of decomposition of HNO₂ to form HNO₃ increases. When ω(H₂O) is 0.2 or 1.0%, the intermediate products are N₂O₄H₂O or N₂O₄(H₂O)₂, respectively, and the reaction proceeds along two paths; when ω(H₂O) ≥ 2.0%, N₂O₄(H₂O)₃ appears as the intermediate product, HNO₃ and HNO₂ are directly produced in one step, and a stable current loop can be formed within the whole system.