Decomposition Mechanism of 5,5′-Bis(tetrazole)-1,1′-diolate(TKX-50) Anion Initiated by Intramolecular Oxygen Transfer

The σ+π dual aromaticity of typical bi-tetrazole ring molecule TKX-50

Two complexes of dihydroxylammonium 5,5'-bistetrazole-1,1'-diolate (TKX-50) were employed to evaluate the aromaticity of their tetrazole rings via deep analysis such as the electronic structure, the ZZ component of the natural chemical shielding tensor (NICSZZ) and component orbitals, localized orbital locator purely contributed by σ-orbitals (LOL-σ) and localized orbital locator purely contributed by π-orbitals (LOL-π), the anisotropy of the induced current density (AICD) and the ZZ component of iso-chemical shielding surface (ICSSZZ) of these tetrazole rings thereof. The conclusion shows: that all tetrazole rings and bi-tetrazole rings in complexes have strong σ and a comparable strength π double aromaticity; all these magnetic shields almost symmetrically increase from the central axis to the tetrazole ring atoms; tetrazole rings in complex II show a little stronger dual aromaticity than that in complex I mainly due to the different orientation of the fragment 2 encompassing two hydroxylamine groups resulting in different effects on the contributions of σ orbitals and π orbitals to total aromaticity of tetrazole rings thereof; the difference in aromaticity is fundamentally caused by the atoms O with stronger electron-withdrawing than atom N in fragment 2 interact with bi-tetrazole ring through O in complex I but through N in complex II.

Analysis of the initial reaction mechanism of TKX-50 based on Raman intensity

CONTEXT

Dihydroxylammonium 5,5'-biotetrazolium-1,1'-diolate (TKX-50) has two important properties of typical azole energy-containing ionic salts, including high energy and safety. Therefore, in today's era where more emphasis is placed on explosive performance and explosive detonation control conditions, TKX-50 is a very important object of research, and its reaction process in the initial stage of detonation is gradually receiving more and more attention from researchers in the field of energy-containing materials research.

METHODS

In this paper, based on first-principles density-functional theory (DFT), the mechanism of chemical bond breakage of TKX-50 under pressure was determined based on the analysis of the strength and stability of chemical bonds inside the TKX-50 molecules using Raman spectroscopy relative intensity analysis. The results show that TKX-50 is dominated by N-H bond breaking and followed by H-O bond breaking in the initial reaction stage. These reactions lead to the reorganization and structural changes within the molecule, which eventually lead to the decomposition of TKX-50.

Atomic perspective revealing for combustion evolution of nitromethane/nano-aluminum hydride composite

Adding aluminum hydride (AlH₃) into energetic materials (EMs) can improve their combustion and energy performance effectively. However, the potential mechanism of AlH₃ on EMs is still unclear. Based on the ReaxFF-lg method, the thermal decomposition of nitromethane/nano-aluminum hydride (NM/nano-AlH₃) composites were studied. The addition of AlH₃ reduces the energy barrier and increases the energy release during the decomposition of NM, accelerates the decomposition of NM. The main way of AlH₃ oxidation involves the capture of O atoms from NM. The results show that AlH₃ content and passivated layer affect the oxidation and hydrogen release of AlH₃. The explosion of small particle size AlH₃ leads to rapid oxidation and hydrogen release. The oxidation of large particle size AlH₃ is dominated by the inward and outward diffusion of O and Al atoms. The products of NM/nano-AlH₃ composites are H₂O, CO₂, N₂ gases, and Al clusters. This work is expected to guide the application of AlH₃ in EMs.