High-Pressure Studies of Hydrogen-Bonded Energetic Material 3,6-Dihydrazino-<i>s</i>-tetrazine Using DFT

Abstract

Hydrogen bonding is an important noncovalent interaction that plays a key role in most of the CHNO-based energetic materials, which has a great impact on the structural, stability, and vibrational properties. By analyzing the structural changes, IR spectra, and the Hirshfeld surfaces, we investigated the high-pressure behavior of 3,6-dihydrazino-<i>s</i>-tetrazine (DHT) to provide detailed description of hydrogen bonding interactions using dispersion-corrected density functional theory. The strengthening of hydrogen bonding is observed by the pressure-induced weakening of covalent N-H bonds, which is consistent with the red shift of NH/NH₂ stretching vibrational modes. The intermolecular interactions in DHT crystals lead to more compact and stable structures that can increase the density but diminish the heat of detonation, <i>Q</i>. The calculated detonation properties of DHT (<i>D</i> = 7.62 km/s, <i>P</i> = 25.19 GPa) are slightly smaller than those of a similar explosive 3,6-bis-nitroguanyl-1,2,4,5-tetrazine (<i>D</i> = 7.9 km/s, <i>P</i> = 27.36 GPa). Overall, the crystallographic and spectroscopic results along with Hirshfeld surface analysis as a function of pressure reveal the presence of strong hydrogen bonding networks in the crystal structure of DHT.