The main challenge for achieving better energetic materials is to increase their density. In this paper, cocrystals of HNIW (2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane, often referred to as CL-20) with TNT (2,4,6-trinitrotoluene) were synthesized using ethanol in a green chemical method. The cocrystal was formulated as C₁₃H₁₁N₁₅O₁₈ and possesses a higher density (1.934 g cm⁻³) than published previously (1.846 g cm⁻³). This high-density cocrystal possesses a new structure, which can be substantiated by the different types of hydrogen bonds. The predominant driving forces that connect HNIW with TNT in the new cocrystal were studied at ambient conditions using single-crystal X-ray diffraction, powder X-ray diffraction, Fourier transform–infrared spectroscopy and Raman spectroscopy. The results reveal that the structure of the new HNIW/TNT cocrystals consists of three one-dimensional hydrogen-bonded chains exploiting the familiar HNIW–TNT multi-component supramolecular structure, in which two hydrogen-bonded chains are between —NO₂ (HNIW) and —CH (TNT), and one hydrogen-bonded chain is between —CH (HNIW) and —NO₂ (TNT). The changes to the electron binding energy and type of element in the new cocrystal were traced using X-ray photoelectron spectroscopy. Meanwhile, the physicochemical characteristics alter after cocrystallization due to the hydrogen bonding. It was found that the new HNIW/TNT cocrystal is more thermodynamically stable than HNIW. Thermodynamic aspects of new cocrystal decomposition are investigated in order to explain this observation. The detonation velocity of new HNIW/TNT cocrystals is 8631 m s⁻¹, close to that of HNIW, whereas the mechanical sensitivity is lower than HNIW.

Nitrogen-rich heterocyclic compounds are important heterocyclic substances with extensive future applications for energetic materials due to their outstanding density and excellent physicochemical properties. However, the weak intermolecular interactions of these compounds are not clear, which severely limits their widespread application. Three nitrogen-rich heterocyclic compounds were chosen to detect their molecular geometry, stacking mode and intermolecular interactions by crystal structure, Hirshfeld surface, RDG and ESP. The results show that all atoms in each molecule are coplanar and that the stacking mode of the three crystals is a planar layer style. A large amount of inter- and intramolecular interaction exists in the three crystals. All principal types of intermolecular contacts in the three crystals are N···H interactions and they account for 40.9%, 38.9% and 32.9%, respectively. Hydrogen bonding, vdW interactions and steric effects in Crystal c are stronger than in Crystals a and b. The negative ESPs all concentrate on the nitrogen atoms in the three molecules. This work is expected to benefit the crystal engineering of heterocyclic energetic materials.

The crystal and molecular structures, intermolecular interactions, and energy of CL-20, HATO, and FOX-7 were comparatively predicted based on molecular dynamic (MD) simulations. By comparison, the 2D fingerprint plot, Hirshfeld surface, reduced density gradient isosurface, and electrostatic potential surface were studied to detect the intermolecular interactions. Meanwhile, the effects of vacuum and different solvents on the crystal habit of CL-20, HATO, and FOX-7 were studied by AE and MAE model, respectively. The energy calculation was also analysed based on the equilibrium structures of these crystal models by MD simulations. Our results would provide fundamental insights for the crystal engineering of energetic materials.