典 型 笼 状 含 能 材 料 晶 体 早 期 冲 击 反 应 的 从 头 算 分 子 动 力 学 模 拟

Energetic molecules with cage-like backbones，owning additional strain energy and stability，are potential candidates for optimizing the long-known contradiction between high energy density and low sensitivity of energetic materials. However，the reaction mechanism of caged energetic materials under shock compression is still unclear. Here，a series of ab initio molecular dynamics calculations were conducted to simulate the early decay of typical caged energetic compounds when compressed by shock waves of 8 to 11 km·s^-1，and the studied compounds included octanitrocubane（ONC），hexanitrohexaazaisowoodethane（CL-20），4，10-dinitro-2，6，8，12-tetraoxa-4，10-diazatetracyclododecane（TEX），and the reference plane system triamino-trinitrobenzene（TATB）. The shock sensitivity of the four studied systems was calculated as ONC > CL-20 > TEX > TATB，which is in good agreement with reference experimental shock/impact sensitivity tests. The reaction initiation mechanism was revealed （i）the presence of electron-rich oxygen/nitrogen elements increases electron delocalization over the cage and the proper degree of freedom of the covalent bonds confers them additional elastic deformation capacity upon shock stimulus，both enhance the structural stability of hetero-cage，（ii）the dissociation of the nitro groups takes precedence over the collapse of the hetero-cage，which can delay the reaction process and reduce the shock sensitivity，and（iii）intermolecular hydrogen bonds（HB）is highly plastic deformable and enriched HB can delay the onset of reactions by buffering shocks. The current study proposed that the hetero-cage backbone with enhanced electron delocalization effect and proper degree of freedom，and the enriched intermolecular hydrogen bonding interactions could reduce the shock wave sensitivity，thereby providing theoretical guidance for the rational design of novel insensitive energetic materials.