Acta Chim. Sinica ›› 2016, Vol. 74 ›› Issue (7): 612-619.DOI: 10.6023/A16030141 Previous Articles     Next Articles

Article

CL20/DNB共晶的热感度分子动力学研究

杨镇, 薛一江, 何远航   

  1. 北京理工大学 爆炸与科学国家重点实验室 北京 100081
  • 收稿日期:2016-03-22 出版日期:2016-07-15 发布日期:2016-06-07
  • 通讯作者: 何远航 E-mail:heyuanhang@bit.edu.cn

Thermal Sensitivity of CL20/DNB Co-crystal Research via Molecular Dynamics Simulations

Yang Zhen, Xue Yijiang, He Yuanhang   

  1. State Key Laboratory of Explosion Science and Technology, Beijing Institute of Technology, Beijing 100081, China
  • Received:2016-03-22 Online:2016-07-15 Published:2016-06-07

Co-crystal technology has effectively improved the safety of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12- hexaazaisowurtzitane (CL20) and retained high detonation velocity, detonation pressure and other properties of CL20. To study why thermal sensitivity of CL20/1,3-dinitrobenzene (DNB) co-crystal can be effectively reduced, simulations of the pyrolysis process of CL20/DNB co-crystal, CL20/TNT co-crystal, CL20 crystal and DNB crystal system were made with ReaxFF/lg force field reactive molecular dynamics in this paper. This paper provides from atomic level detailed information on thermal decomposition processes of CL20, DNB, CL20/DNB co-crystal and CL20/TNT co-crystal such as reaction pathway, contributing to a better understanding of differences between co-crystal and pure crystal. The results show that CL20/DNB co-crystal has lower thermal sensitivity than CL20 and CL20/TNT co-crystal, but has higher thermal sensitivity than DNB, which is consistent with experimental data. Besides, the initial reaction pathways of CL20 and CL20/DNB were found, which reveals the reasons why co-crystal can effectively reduce CL20 thermal sensitivity. CL20 and CL20/DNB have similar initial reaction pathways: N—NO2 bond of CL20 molecules breaks, working as a dominant role in the initial stage of thermal decomposition under the condition of different temperatures, followed by cage skeleton structure breaking reaction. We found two reasons for the decrease rate of CL20 in CL20/DNB co-crystal decomposition: (A) The huge number of DNB molecules in the initial reaction stage prevents effective collision between CL20 and the intermediate reactants, thus lowering the speed of CL20 thermal decomposition. (B) Part of DNB molecules react with CL20 molecules and the intermediate products, producing C6H4N3O6, C6H4N4O8 and C10H10N14O16 etc., which decrease concentration of CL20. Both are explanations from microscopic mechanism on why the thermal sensitivity of CL20/DNB co-crystal is lower than that of CL20 crystal. In addition, CL20/DNB co-crystal and CL20 have similar main reactants, such as NO2, NO3, N2, N2O2, HNO, H2O, CO2, and HONO etc. Through the analysis of the reaction kinetics, we obtain activation barrier of CL20 system and CL20/DNB system. This study confirms the fact that co-crystallization is an effective way to decrease the thermal sensitivity for CL20 while retaining high detonation performance.

Key words: ReaxFF/lg, molecular dynamics, CL20/DNB co-crystal, reaction mechanism, thermal sensitivity