Categorizing and Understanding Energetic Crystals

The subject of energetic crystals has been significantly enriched in the past several decades, with the number rising rapidly. Meanwhile, some new types of crystals have appeared, such as energetic extended solids, energetic ionic salts, energetic metal organic frames, energetic cocrystals, metallic hydrogen, and energetic perovskites. They may dazzle us but give rise to a difficulty in understanding these compounds and work to achieve general knowledge from them and design new ones; thus, it becomes interesting and crucial to categorize energetic crystals. In this work, on the basis of the types of primary constituent parts and their interactions in crystal, we classify experimentally observed and theoretically predicted energetic crystals into five types, including molecular crystal, ionic crystal, atomic crystal, metallic crystal, and mixed-type crystal; i.e., energetic crystals cover all the five crystal types and exhibit a high diversity. By categorization, it will become much easier to understand and predict various formation and energy release mechanisms of energetic crystals. Furthermore, a dependence of energy level on crystal type is summarized, as the energy content increase follows an order of molecular crystal, ionic crystal and mixed type crystal, atomic crystal, and metallic crystal. In general, a highly energetic crystal should exist under high pressure, while a crystal with a moderate or low energy content can exist under common conditions. Thus, this work presents an overall perspective on the crystal structures of energetic materials and makes the increasing energetic crystals roughly and readily understandable, despite the increasing diversity and complexity of these structures.

Automated summary

By categorizing energetic crystals into different types based on their primary constituent parts and interactions in crystals, we have gained a clearer understanding of these compounds, making it easier to comprehend and predict the formation and energy release mechanisms of energetic crystals.