Impact-induced mechanical and chemical responses of cyclobutane nitric ester isomers: a reactive molecular dynamics study

Cyclobutane nitric esters represent a new class of molecular energetic materials whose stereo- and regiochemical configurations critically affect their mechanical response and decomposition reactivity. However, the microscopic mechanisms governing their behavior under localized impact remain poorly understood. In this work, molecular dynamics were employed to investigate the mechanical deformation, energy dissipation, and chemical activation of several TNCBNE isomers subjected to diamond-sphere impact loading. A clear three-stage impact response is identified, including elastic compression, plastic deformation, and structural failure. The local build-up of kinetic energy forms small hotspots where the temperature and stress become highly concentrated, creating the main sites for bond breaking. Once these hotspots appear, the chemical reactions begin with strain-driven O-NO₂ bond cleavage and then continue with backbone fracture and ring opening. Besides, the k and extent exhibit pronounced isomer dependence, as reflected by distinct αN₂/N₃ evolution trends. Iso-2 and iso-7 show faster nitro activation and higher αN₂/N₃ ratios, whereas iso-3 and iso-5 display delayed O-NO₂ cleavage and reduced sensitivity. These results reveal a clear link between the molecular structure, energy localization, and reaction sensitivity, giving an atomic-level view of how molecular geometry controls impact-induced decomposition in cyclobutane nitric esters.