Different Stoichiometric Ratios Realized in Energetic–Energetic Cocrystals Based on CL-20 and 4,5-MDNI: A Smart Strategy to Tune Performance

A new 1:3 CL-20 (2,4,6,8,10,12-hexanitrohexaazaisowurtzitane)/4,5-MDNI (1-methyl-4,5-dinitroimidazole) cocrystal ( 1 ) in combination with the previously reported 1:1 CL-20/4,5-MDNI cocrystal ( 2 ) together have been first realized in different stoichiometric ratios based on CL-20 and 4,5-MDNI in energetic–energetic cocrystals. Subtle differences in intermolecular interactions and packing motifs may lead to the formations of the cocrystals 1 and 2 by structure comparisons. Moreover, properties (e.g., density, thermal properties, sensitivity, and detonation performances) varied significantly under different stoichiometric ratios and crystal structures. For instance, the comprehensive performances of cocrystal 1 (ρ: 1.813 g/cm 3; D: 8604 m/s, P: 34.45 GPa; IS: 16 J) were less excellent than those of cocrystal 2, whereas cocrystal 1 exhibited a detonation velocity superior to that of LLM-105 (2,6-diamino-3,5-dinitropyrazine-l-oxide, a relatively new insensitive explosive) and a low impact sensitivity close to that of LLM-105; thus, cocrystal 1 may act as a new high-energy insensitive explosive. Moreover, the findings of CL-20/4,5-MDNI cocrystals may offer new insights into the design and preparation of energetic cocrystals with different ratios and other energetic cocrystals, enrich better understanding of the formations for energetic cocrystals, and provide a smart strategy to tune performances.