Structural transformation of energetic cyclo-pentazolate salt under the pressure
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ORIGINAL RESEARCH
Structural transformation of energetic cyclo-pentazolate salt under the pressure Yunqiu Li 1 & Bin Li 1 & Lifeng Xie 1 Received: 20 March 2020 / Accepted: 22 April 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract The density functional theory (DFT) was applied to investigate the structure, optical properties, and non-bonded interactions of the cyclo-pentazolate salt [Mg(H2O)6(N5)2]·4H2O in the pressure range of 0–100 GPa. The results show that there is a structural transition at the pressure of 64 GPa, which has not been found in the experiments. As the pressure increases, the band gap gradually decreases with a sudden increase at the structural transition point. The analysis of DOS presents that the electronic localization in the crystal gradually weakens under the pressure. The structural transition point also exists in the hydrogen bonds and the Hirshfeld surfaces under compression. The absorption spectra of the cyclo-pentazolate salt at high pressures show some strong bands in the fundamental absorption region. The increasing pressure helps to improve the photoelectric performances of the crystal. Our studies are expected to provide a new understanding of the structural transition of the novel energetic materials under high pressures. Keywords DFT . Structural transition . Cyclo-pentazolate salt . Hydrogen bonds . Pressure
Introduction Solid propellant has been widely used in space delivery and strategic and tactical missile systems [1–6]. However, the next generation of strategic weapons puts forward higher demand for propulsion technology. It is difficult for the traditional energetic compounds containing C, H, O, and N to meet the demands in the future. The new concept of ultra-high energy density materials becomes the most promising energetic compounds for solid propellants. Therefore, the study of all nitrogen pentazole compounds is particularly noticeable. Pentazole compounds have the advantages of high density, high heat of formation, high gas yield, low sensitivity, and cleanliness of detonation products, which make them effective, safe, and environmentally friendly candidates for high energy density materials (HEDMs) [7–13]. Therefore, pentazole compounds as potential energetic materials have attracted great attention owing to their broad application prospects in the field of
* Lifeng Xie [email protected] 1
Department of Safety Engineering, School of Chemical Engineering, Nanjing University of Science and Technology, Nanjing 210094, China
explosives, propellants, and other energetic materials in the future. However, the development of all nitrogen pentazole compounds has gone through a long and tortuous course. Huisgen and Ugi [14] successfully synthesized aryl pentazole compounds with aryl diazo salts and sodium azide for the first time at low temperature of − 35 °C, thus opening the prelude of cycloaddition to pentazole compounds. However, due to the very unstable nature of pentazole ring, the subsequent synthesis studies have been stagna
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