Uncovering the Morphological Regulation Mechanism of Low Sensitivity and Highly Energetic Materials in Solvents: Changing Crystal Morphology Induced by Hydrogen Bonding

Abstract

Low sensitivity and highly energetic materials (LSHEMs) are currently the most promising high-energy materials due to their structural stability. However, many problems exist due to their abundant hydrogen bonding (HB) in the structure, such as low solubility and difficulty controlling the crystallization process. In this paper, aiming at regulating the crystal morphology of LSHEMs, 4,4′,5,5′-tetranitro-1H,1′H-[2,2′-biimidazole]-1,1′-diamine is used as a model substance to explore the mechanism of controlling the crystal morphology in solvents. The molecular structure, crystal structure, and HB sites on crystal faces were investigated by molecular electrostatic potential surface, Hirshfeld surface, and HB analyses, and it was found that the HB density [δ(HB)] of faces is of the order (011) > (11−1) > ( 110) > (100) in crystal or solution, determining the tendency of interaction with polar solvents. Then, using molecular dynamics simulation and the modified attachment energy model, we found that the attachment energy of crystal faces and the predicted crystal morphologies in different solvents were determined by HB sites on faces and strongly correlated with the solvent polarity. The experimental morphologies were consistent with the trend predicted including the aspect ratio trend, which confirmed our theoretical speculation. This work provides an effective method of choosing solvents for morphology customization of LSHEMs, which will help guide the morphology control and realize the industry application of LSHEMs.

Morphology Prediction Methods and Their Applications in Energetic Crystals

“…In recent years, the application of morphology prediction models, such as the MAE models, ,− growth mechanistic model, , and dynamic Monte Carlo simulation method, has become increasing popular. Morphology prediction models have been also widely applied in energetic crystals grown under various conditions, such as vacuum, solvents, and additives, with effects of temperature, volume ratio of mixed solvents, supersaturation, and other conditions covered. − Also, this research revealed the growth mechanism of energetic crystals at the microscopic level, which presented theoretical guidance for morphology control. Meanwhile, valid force fields are important for the specified energetic compounds.…”

“…Still, the characteristics of the component and packing structure of a crystal face are widely adopted to understand a crystal growth mechanism and to guide the selections of solvent and modifier. For example, Liu et al considered the packing structure of a crystal face to accurately predict the morphology of some energetic crystals, , and Wang et al adopted the hydrogen bonding density to uncover the morphological regulation mechanism of low sensitivity and highly energetic materials in solvents . Besides, the crystal packing structure is considered in all the aforementioned models, showing its importance therein.…”

The effect of solvent–crystal interaction on the morphology of a solvate of rifampicin

“…Among these exposed crystal faces, the (0 −2 0) and (0 2 0) faces have the minimum absolute adhesion energy (−95.24 Hirshfeld surface (HS) analysis [34][35][36][37] has been used to investigate intermolecular interactions, and could directly discern the intermolecular interaction sites in a crystal. 38,39 The Hirshfeld surface of the rifampicin molecule is displayed in Fig. 5(a), where the red and blue stand for high and low close contact populations, respectively.…”

Understanding the Relationship between Molecular Assembly and Polymorph Selection of 4,4′,5,5′-Tetranitro-1H,1′H-[2,2′-biimidazole]-1,1′-diamine in Solution

“…Following its synthesis by Breiner’s group in 2013, DATNBI has been noted for its excellent explosive performance and safety, and its crystal structures have been progressively uncovered in recent years. Currently, form α and form β are the discovered polymorphs of DATNBI, with form α identified as a rare polymorph in extensive experiments. , Moreover, many studies found that the dimer structures are relevant to nuclei structure and affect the polymorphism. − In our previous research, the existence of hydrogen bonding dimers of DATNBI in solution was demonstrated using DFT and infrared spectroscopy and was found to play a decisive role in the DATNBI solid forms . Therefore, we hypothesized that the shape of the dimer assembly may be a good model for the polymorph selection.…”

“…Currently, form α 30 and form β 31 are the discovered polymorphs of DATNBI, with form α identified as a rare polymorph in extensive experiments. 32,33 Moreover, many studies found that the dimer structures are relevant to nuclei structure and affect the polymorphism. 34−36 In our previous research, the existence of hydrogen bonding dimers of DATNBI in solution was demonstrated using DFT and infrared spectroscopy and was found to play a decisive role in the DATNBI solid forms.…”