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| - Theoretical Studies on the Structures, Thermodynamic Properties, Detonation Properties,and Pyrolysis Mechanisms of Spiro Nitramines
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| - Density function theory (DFT) has been employed to study the geometric and electronic structures of a seriesof spiro nitramines at the B3LYP/6-31G** level. The calculated results agree reasonably with availableexperimental data. Thermodynamic properties derived from the infrared spectra on the basis of statisticalthermodynamic principles are linearly correlated with the number of nitramine groups as well as the temperature.Detonation performances were evaluated by the Kamlet-Jacobs equations based on the calculated densitiesand heats of formation. It is found that some compounds with the predicted densities of ca. 1.9 g/cm3, detonationvelocities over 9 km/s, and detonation pressures of about 39 GPa (some even over 40 GPa) may be novelpotential candidates of high energy density materials (HEDMs). Thermal stability and the pyrolysis mechanismof the title compounds were investigated by calculating the bond dissociation energies (BDE) at the B3LYP/6-31G** level and the activation energies (Ea) with the selected PM3 semiempirical molecular orbital (MO)based on the unrestricted Hartree−Fock model. The relationships between BDE, Ea, and the electronic structuresof the spiro nitramines were discussed in detail. Thermal stabilities and decomposition mechanisms of thetitle compounds derived from the B3LYP/6-31G** BDE and the UHF−PM3 Ea are basically consistent.Considering the thermal stability, TNSHe (tetranitrotetraazaspirohexane), TNSH (tetranitrotetraazaspiroheptane),and TNSO (tetranitrotetraazaspirooctane) are recommended as the preferred candidates of HEDMs. Theseresults may provide basic information for the molecular design of HEDMs.
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