Molecular Design And Properties Of Oxadiazole Based Energetic Materials

Nitrogen-rich compounds with high energy density are an important research content in the field of energetic materials,and the study of their structures and properties are particularly important.Nitrogen-rich heterocyclic compounds can not only improve the heats of formation of energetic compounds,but also improve their detonation properties during the process of combustion and explosion.Therefore,it is an important factor to be considered in the design of energetic materials.In this paper,three different energetic compounds were designed based on nitrogen-rich parent oxadiazole.The structures of the compounds were optimized on the B3LYP/6-311G（d,p）basis set level by using the density functional theory（DFT）of quantum chemistry.The heats of formation and detonation properties of the designed compounds were calculated by designing the isodesmic reactions and the Kamlet-Jacobs equation.The thermal stabilities of the designed compounds were preliminarily predicted by calculating their bond dissociation energies.Finally,a series of potential high energy compounds were screened and their electronic structures were studied.The main content of this paper is as follows:In the first part,48 kinds of 1,2,5-oxadiazole bridged compounds with symmetrical structures were designed.The energy gaps,heats of formation,detonation properties and thermal stabilities of these compounds have been studied at the B3LYP/6-311G（d,p）level using density functional theory.The results show that the heats of formation of these compounds are from 225.9 to 1260.7 k J mol^-1,the detonation velocity is from 5.89to 9.61 km s^-1,and the detonation pressure is from 13.8 to 43.2 GPa.The-C（NO₂）₃ and-N=N-groups can significantly improve the detonation properties of these compounds,while the introduction of-NH-NH-bridge can significantly reduce their thermal stability.In consideration of their detonation property and thermal stability,four compounds（B8,D8,E8 and F8）were selected as potential energetic compounds with excellent detonation properties and acceptable stabilities,and their electronic structures were studied.In the second part,64 bridged compounds were designed based on 1,3,4-oxadiazole and 1,2,5-oxadiazole,which are more stable compared to other oxadiazole isomers.The energy gaps,heats of formation,detonation properties and thermal stabilities of these compounds have been studied at the B3LYP/6-311G（d,p）level using density functional theory.The results show that the heats of formation of these compounds are from 62.7to 1094.2 k J mol^-1,the detonation velocity is from 5.71 to 9.51 km s^-1,and the detonation pressure is from 13.0 to 42.3 GPa.The heats of formation and detonation properties of the compounds are obviously improved by-N=N-bridge.Based on comprehensive consideration of detonation property and thermal stability,five energetic compounds（C8,E8,F8,G8 and H8）were selected as potential energetic compounds with excellent detonation propertiesand acceptable stabilities,and their electronic structures were further studied.In the third part,64 bridged energetic compounds were designed based on 1,2,3,4-tetrazole and 1,2,5-oxadiazole.The energy gaps,heats of formation,detonation properties and thermal stabilities of these compounds have been studied at the B3LYP/6-311G（d,p）level using density functional theory.The results show that the heats of formation of these compounds are from 454.7 to 1506.3 k J mol^-1,the detonation velocity is from 6.26 to 9.52 km s^-1,and the detonation pressure is from 15.7to 42.1 GPa.The-N=N-and-N₃ groups can obviously increase the heats of formation of the compounds.The variation trends of density,detonation pressure and detonation velocity are basically the same,indicating that density is the key parameter to determine detonation performance.From the point view of bond dissociation energy,-CN/-NH₂substituent can improve the thermal stabilities of the designed compound.Consideration of detonation property and thermal stability,seven energetic compounds（B8,C8,D8,E8,F8,G8 and H8）were selected as potential energetic compounds with excellent detonation properties and acceptable stabilities,and their electronic structures were further studied.