The Response of Four Energetic Compound Molecules to Ultraviolet Light Using TDDFT

The time-dependent density functional theory (TDDFT) was used to study the light absorption spectra of 3-nitro-1, 2,4-triazol-5-one (NTO) , 1 ,3 ,5-trinitroperhydro-1 ,3 ,5-triazine (RDX) , 1 ,3 ,5 ,7-tetranitrooctahydro-1 ,3 ,5 ,7-tetrazocine (HMX) and 2,4,6,8,10, 12-hexanitro-2,4, 6,8, 10, 12-hexaazatetracyclo[5.5.0.0(3, 11).0(5, 9)]dodecane (CL-20) molecules, the evolution of molecular structure and differential charge density with time under Ultraviolet (UV) light.The sensitivity trends of TDDFT compared with the simulation results show that the number of excited-state electrons under UV light may serve as descriptors of electronic stability, where the electronic stability rank is NTO>CL-20>HMX>RDX.The ease of nitro group detachment under ultraviolet excitation may serve as descriptors of irradiation sensitivity in molecular level, where the irradiation sensitivity rank is CL-20-RDX>HMX>NTO.And NTO molecule exhibits the lowest irradiation sensitivity.Under UV light, these four explosive molecules undergo several main reactions, including dehydrogenation, ring opening, nitro group separation, and nitro group deoxygenation, to form nitrogen gas.The excited nitro group, known for its strong electron-withdrawing properties, plays a crucial role in electron transfer to the surrounding environment.The extent of charge transfer on the nitro group varies with light intensity, leading to the different decomposition products.The simulation results demonstrate that under weak light fields, nitro groups dissociate to form nitrogen dioxide, with the main decomposition products being nitrogen dioxide and hydrogen radicals.However, some nitro groups undergo deoxygenation to form nitrous groups when exposed to intense light.If the dissociation energy of the nitro group is sufficiently high, complete deoxygenation can occur, causing the nitro group to detach from the ring structure and form nitrogen.The intermediate products of the reaction include hydrogen, oxygen free radicals, nitrogen dioxide, nitroso, and nitrogen molecules.