A Theoretical Comparative Study on Thermal Stabilities of Ammonium Pentazolate and Its Cocrystals

Pentazolate compounds have garnered considerable interest as promising building blocks for novel polynitrogen compounds. Leveraging insights from the study of other energetic materials, researchers have enhanced the thermal stability of pentazolate compounds by synthesizing cocrystals, thereby addressing the issue of their poor thermal stability. In this study, the thermal decomposition mechanism of NH₄N₅ and its cocrystals ((N₅)₆(H₃O)₃(NH₄)₄Cl and NH₄N₅·1/6NH₄Cl) was investigated from a theoretical perspective. Laplace bond orders, decomposition pathways, transition states, interaction energies, and aromaticity were employed in the analysis. The computational results indicate that the asymmetric structure R3 of NH₄N₅·1/6NH₄Cl demonstrated incredible thermal stability and aromaticity, with a minimum Laplacian bond order of 1.036, a decomposition barrier of 29.48 kcal mol⁻¹, and an ELF-π value of 0.719. Therefore, co-crystallization with high-energy materials with high decomposition temperatures can enhance the thermal stability of pentazolate compounds.