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Energetic cocrystallization is a promising crystal engineering method for energetic materials. However, the current yield of energetic–energetic cocrystals (EECCs) remains very limited largely as a result of inefficient EECC screening. Therefore, the crystallization thermodynamics of EECCs must be predicted; this process is the core of the screening procedure. The present work provides insight into the intermolecular interactions of and variations in lattice energy, enthalpy, and Gibbs free energy following the crystallization of observed and supposed EECCs. Moreover, this research clarifies the difference in the solubility parameters of each pair of coformers. As a result, formation is predicted to be thermodynamically favored for most observed and supposed EECCs. The dominance of entropy is more sufficient than that of enthalpy; this dominance is mainly caused by the structural similarity in energetic molecules that either produce little heat or absorb heat if an intermolecular rearrangement is observed to transform pure crystals into cocrystals. Implicitly, EECCs can be formed efficiently when confusion degrees or spatial molecular configurations increase, thus guaranteeing entropy dominance.

2,4,6,8-Hexanitro-2,4,6,8,10,12-hexaazatetracyclododecane (CL-20) is the most powerful explosive applied, and CL-20-based energetic–energetic co-crystals are promising new alternative explosives with tunable power and safety, resulting in much interest in them. This work discusses the structural, electronic and energetic features of three CL-20 polymorphs, β, γ and e forms, and three CL-20-based energetic–energetic co-crystals, CL-20/TNT, CL-20/HMX and CL-20/BTF. As a result, we find that, relative to the pure CL-20 polymorphs, the co-crystallization of CL-20 with HMX, TNT and BTF cause little molecular deformation except from some torsion of its nitro groups, and the narrower band gaps. And dominantly, the O⋯O, O⋯H and O⋯N interactions hold all the crystal packing. There is possibly thermodynamic and kinetic dominance in the CL-20/TNT and CL-20/HMX, and CL-20/BTF co-crystallization, respectively, in terms of their formation energy. Further, a rough criterion for predicting energetic co-crystal formation is obtained, as the solubility parameter difference of two coformers of a binary energetic co-crystal is less than 8 MPa0.5.

Energetic cocrystals are attracting increasing attention in the field of energetic materials. To low-sensitive and high energetic materials, we provide the evaluations of power and safety of 41 observed binary energetic cocrystals, by studying their densi

Intermolecular friction (IF) is an important but unclear concept in the material world. We propose intermolecular friction symbols (IFSs) to straightforwardly and roughly evaluate IF in crystal bulks and introduce a method for plotting them in terms of th