Effects of oxidizing molecules on the thermal decomposition of TTDO by ab initio molecular dynamics simulations

Oxidizing molecules play a very important role in improving the comprehensive properties of energetic materials. Recently, a series of energetic cocrystals containing 2,4,6-triamino-1,3,5-triazine-1,3-dioxide (TTDO) and oxidizing molecule have been successfully prepared. Therefore, ab initio molecular dynamics were used to simulate the thermal decomposition process of TTDO, TTDO:H₂O₂, TTDO:HNO₃, and TTDO:HClO₄ crystals at 3000 K to study the role of oxidizing molecules during the thermal decomposition of TTDO. The initial decomposition paths of the TTDO crystal include N-H bond breaking, C-N bond breaking, and intramolecular and intermolecular H transfers. The formation mechanisms of H₂O, N₂, and CO₂ in the four crystals are completely different. The key formation mechanism of H₂O is the combination of O with OH, that of N₂ is the formation of the -N-N- structure, and that of CO₂ is to form the intermediate CO-R with carbonyl structure that form the fragment with the -O-C-O- structure. All the oxidizers H₂O₂, HNO₃, and HClO₄ involve in the formation of H₂O, N₂, and CO₂. The formation mechanisms of urea during the decomposition process of the four crystals are completely different, but the key step is to produce the structure of -N-CO-N-. An analysis of N_x shows that H₂O₂, HNO₃ and HClO₄ affect not only the types of N_x, but also its formation mechanisms. Among them, HNO₃ has the greatest influence on N_x.

The Raman and IR vibration modes of metal pentazolate hydrates [Na(H2O)(N5)]·2H2O and [Mg(H2O)6(N5)2]·4H2O

The detailed illustrations of the structures, elastic properties, and Raman and IR vibration modes for [Na(H₂O)(N₅)]·2H₂O (a) and [Mg(H₂O)₆(N₅)₂]·4H₂O (b) have been presented in this investigation by using the first-principles method based on the density functional theory. Our results indicate that the active centers of both two types of the energetic metal pentazolate hydrates appear on the cyclo-N₅. The bonding character of N atoms in the cyclo-N₅ is shown to be covalent, and the cyclo-N₅ ring can be considered as an anion. Based on the analysis of elastic properties, we conclude that complex a is easier to deform than b, and both complexes are mechanically stable. From the calculated Raman and IR vibration modes, the vibration in the region of 960-1206 cm^-1 (for a) and 985-1208 cm^-1 (for b) is determined by basically mixing the cyclo-N₅ stretching and deformation modes. The vibrational modes of a and b in their highest frequency zones are both related to the stretching of the O-H bonds.

N⁻₃ azide anion confined inside finite-size carbon nanotubes

In this work, the confinement of an N[Formula: see text] azide anion inside finite-size single-wall zigzag and armchair carbon nanotubes of different diameters has been studied by wave function and density functional theory. Unrelaxed and relaxed interaction energies have been computed, resulting in a favorable interaction between the guest and host system. In particular, the largest interaction has been observed for the confinement in an armchair (5,5) carbon nanotube, for which a natural population analysis as well as an investigation based on the molecular electrostatic potential has been carried out. The nature of the interaction between the two fragments appears to be mainly electrostatic, favored by the enhanced polarizability of the nanotube wall treated as a finite system and passivated by hydrogen atoms. The results obtained are promising for possible applications of this complex as a starting point for the stabilization of larger polynitrogen compounds, suitable as a high-energy density material.