Yuanjie Shu

Crystal morphology of 3,4-bis(3-nitrofurazan-4-yl)furoxan (DNTF) in a solvent system: molecular dynamics simulation and sensitivity study

Herein, the attachment energy (AE) model was employed to study the growth morphology of 3,4-bis(3-nitrofurazan-4-yl)furoxan (DNTF) under vacuum and solvent conditions by molecular dynamics simulation. The DNTF crystals were cultivated in H2O/acetic acid (AcOH) and H2O/EtOH solvents by natural cooling. The calculated results show that the (0 1 1) and (0 0 1) faces have large morphological importance in these two solvent systems, and the predicted DNTF morphologies agree qualitatively with those of the observed experimental results. Radial distribution function (RDF) and diffusion coefficient analyses were performed to explore the adsorption and diffusion behaviors of solvent molecules on DNTF surfaces. Furthermore, the impact and friction sensitivities of different crystal morphologies of DNTF were also tested and discussed. Results suggest that crystal morphology is an important impact factor for controlling the sensitivity of explosives.

Synthesis, structure and properties of neutral energetic materials based on N-functionalization of 3,6-dinitropyrazolo[4,3-c]pyrazole

3,6-Dinitropyrazolo[4,3-c]pyrazole (DNPP, 4) was prepared using an efficient modification process. Various neutral energetic derivatives of DNPP were synthesized from N-functionalization of imide (NH) group. All compounds were fully characterized by 1H and 13C nuclear magnetic resonance spectroscopy, infrared spectroscopy, elemental analysis, and differential scanning calorimetry (DSC). The crystal structures of compounds 4·2H2O, 12 and 15 were confirmed by single-crystal X-ray diffraction, showing extensive hydrogen-bonding. The densities of neutral derivatives ranged from 1.74 to 1.95 g cm−3, and all compounds have positive heats of formation in the range of 18.8 to 863 kJ mol−1. Based on the measured densities and calculated heats of formation, theoretical performance calculations, including detonation pressures (27.1–41.5 GPa) and velocities (7819–9364 m s−1), were carried out using the Gaussian 09 program and Kamlet–Jacobs equations, and they compare favorably with those of TNT and RDX. These properties make them potential and competitive for use as new high energy-density materials.

Comparative study of melting points of 3,4-bis(3-nitrofurazan-4-yl)furoxan (DNTF)/1,3,3-trinitroazetidine (TNAZ) eutectic compositions using molecular dynamic simulations

3,4-Bis(3-nitrofurazan-4-yl)furoxan (DNTF) and 1,3,3-trinitroazetidine (TNAZ) have been widely investigated as important candidate components in melt cast explosives. This paper presents a study of melting point prediction of DNTF/TNAZ eutectic compositions using a molecular dynamics simulations method. The melting points were determined according to the variation of various parameters including specific volume, free volume, diffusion coefficient, specific heat capacity and non-bonded energy, and good agreements were observed from the comparison between calculated values and prevenient experimental data. The binding energies (Ebind) and radial distribution functions (RDFs) were also performed to explore the interactions between DNTF and TNAZ molecules, and results reveal that a weak hydrogen bond from H of TNAZ and O of DNTF vanishes from solid to liquid phase. The detonation performances of DNTF/TNAZ eutectic were also discussed by comparing with other common castable explosives. Results show that the high performance and low melting point make the mixture DNTF/TNAZ (4/6) a good candidate for melt cast explosives. In general, it is worth noting that molecular dynamics simulations provide a useful tool to understand the thermal properties of energetic eutectic compositions.

Synthesis, characterization and properties of heat-resistant explosive materials: polynitroaromatic substituted difurazano[3,4-b:3′,4′-e]pyrazines

The synthesis of three heat-resistant explosive materials: 4,8-di(2,4,6-trinitrophenyl)difurazano[3,4-b:3′,4′-e]pyrazine (1), 4,8-di(2,4-dinitrophenyl)difurazano[3,4-b:3′,4′-e]pyrazine (2), 4-amino-8-(2,4,6-trinitrophenyl)difurazano[3,4-b:3′,4′-e]pyrazine (3),were reported and characterized by 1H NMR,13C NMR, IR as well as elemental analysis. X-ray crystallographic analysis confirmed the structure of 2, as well as displaying intermolecular hydrogen bonding. The thermal behaviors of these compounds were studied with differential scanning calorimetry (DSC) and thermal gravity-differential thermal gravity analysis (TG-DTG) methods. All the compounds showed good thermal stability with exothermic decomposition peaks in the range of 283 °C to 415 °C, on DSC. The sensitivities and calculated explosive performances were also reported for these energetic materials. All the results showed that polynitroaromatic substituted difurazano[3,4-b:3′,4′-e]pyrazines have the potential to be useful heat-resistant explosive materials.

Comparative studies on structure, sensitivity and mechanical properties of CL-20/DNDAP cocrystal and composite by molecular dynamics simulation

Molecular dynamics simulation was performed on 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20), 2,4-dinitro-2,4-diazapentane (DNDAP), and CL-20/DNDAP cocrystal and composite under COMPASS force field at different temperatures. The binding energy (Ebind), radial distribution function (RDF), trigger bond length, cohesive energy density (CED) and mechanical properties were studied and compared. The results show that the binding energy of the cocrystal is evidently higher than that of the composite at the same temperature. RDF analysis reveals that hydrogen bonds and vdW forces between CL-20 and DNDAP exist in both CL-20/DNDAP cocrystal and composite, and the interactions in the cocrystal are stronger than those in the composite. The maximum trigger bond length decreases in the order e-CL-20 > CL-20/DNDAP composite > CL-20/DNDAP cocrystal. Moreover, the rigidity and stiffness of the cocrystal and composite decrease compared to that of CL-20, while the ductility and elasticity are better than that of the two pure components. These results demonstrate that CL-20/DNDAP cocrystal might be very promising in explosive applications.

Direct insight into the formation driving force, sensitivity and detonation performance of the observed CL-20-based energetic cocrystals

2,4,6,8,10,12-Hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) is the most powerful commercially available explosive. This paper discusses the molecular structures and intermolecular interactions of pure e-CL-20 and three CL-20-based energetic–energetic cocrystals, CL-20/2,4-dinitro-2,4-diazapentane (DNDAP), CL-20/2,5-dinitrotoluene (DNT) and CL-20/1-methyl-3,5-dinitro-1,2,4-triazole (MDNT). The underlying mechanisms of their dramatic and divergent sensitivity and detonation performance were revealed as well. We find that CL-20/DNDAP and CL-20/DNT cocrystals arrange in layered motifs, while CL-20/MDNT features irregular but compact packing. Overall, the non-covalent interactions govern the structures of the cocrystals. Regarding sensitivity, in the case of CL-20/DNDAP and CL-20/DNT, the high impact sensitivity of CL-20 is reduced, making the two cocrystals viable explosives. Conversely, CL-20/MDNT uniquely exhibits higher impact sensitivity compared with pure CL-20, which may be caused by weak intermolecular interactions and molecular transformation of CL-20 from stable e-form to α-form. Furthermore, CL-20/MDNT possesses the greatest detonation performance due to its excellent density and high heat of formation, followed by CL-20/DNDAP and CL-20/DNT. These results confirm that a layered packing pattern and weak hydrogen bonding are among the key factors for insensitive cocrystal explosives. Meanwhile, cocrystals of CL-20 with multi-nitrogen energetic compounds have the potential to be promising high-performance energetic materials.