Growth morphology of CL-20/HMX cocrystal explosive: insights from solvent behavior under different temperatures

Abstract

A 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) /1,3,5,7-tetranitro-1,3,5,7-tetrazacyclooctane (HMX)-isopropanol (IPA) interfacial model was constructed to investigate the effect of temperature on cocrystal morphology. A constant volume and temperature molecular dynamics (NVT-MD) simulation was performed on the interfacial model at various temperatures (295-355 K, 20 K intervals). The surface electrostatic potential (ESP) of the CL-20/HMX cocrystal structure and IPA molecule were studied by the B3LYP method at 6-311++G (d, p) level. The surface energies, polarities, adsorption energy, mass density distribution, radial distribution function (RDF), mean square displacement (MSD) and relative changes of attachment energy were analyzed. The results show that polarities of (1 0 0) and (0 1 1) cocrystal surfaces may be more negative and affected by IPA solvent. The adsorption energy per area indicates that growth of the (1 0-2) face in IPA conditions may be more limited, while the (1 0 0) face tends to grow more freely. MSD and diffusion coefficient (D) analyses demonstrated that IPA molecules gather more easily on the cocrystal surface at lower temperatures, and hence have a larger effect on the growth of cocrystal faces. RDF analysis shows that, with the increasing of temperature, the strength of hydrogen bond interactions between cocrystal and solvent becomes stronger, being highest at 335 K for the (1 0 0) and (0 1 1) interfacial models. Results of relative changes of modified attachment energy show that (1 0 0) and (0 1 1) faces tends to be larger than other faces. Moreover, the predicted morphologies at 295 and 355 K are consistent with experimental values, proving that the CL-20/HMX-IPA interfacial model is a reasonable one for this study. Graphical Abstract Construction of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) /1,3,5,7-tetranitro-1,3,5,7-tetrazacyclooctane (HMX)-isopropanol (IPA) interfacial model, analysis, and morphology prediction of cocrystal.

Synthesis, Characterization and Morphological Study of Nicotinamide and <i>p</i>-Coumaric Acid Cocrystal

“…It was observed that NH2, -COOH, and -OH (phenol) groups are exposed on most of the crystal facets. The exposed group may affect the polarities of the crystal facet, which then affects the interaction with the solvent [39][40]. The crystal facet with exposed oxygen atoms (high polarity) will contribute to the high electrostatic energy for the particular facets [53].…”

“…The molecular modeling simulation method is a widely used technique in crystal research [37], commonly used to predict crystal morphology and examine the growth mechanism at the atomistic/molecular level [38]. Validation of the predicted crystal morphology (commonly carried out in a vacuum environment) is a complex and challenging process in which in an actual situation, the crystals are grown in an environment with the presence of solvents and additives [39][40]. Molecular structure of a crystal is packed in a unit cell as a building unit and heavily depending on intermolecular interaction such as hydrogen bond and van der Waals between the molecules and are the important parameters, which affect the crystal shape, and hence the degree of solubility [41].…”

Exploring the effects of solvents on an organic explosive: Insights from the electron structure, electrostatic potential, and conformational transformations of 2,4,6,8,10,12‐hexanitro‐2,4,6,8,10,12‐hexaazaisowurtzitane

“…Research on the morphology and phase purity showed that most solvents yield mixtures of phases of CL‐20, mainly the ε ‐form . The effects of solvents on the growth and morphology of CL‐20‐based cocrystals were also investigated, and the results indicated that the solvents have a cooperative effect in the cocrystallization. Moreover, the potential cocrystal formers of CL‐20 were studied through their molecular electrostatic potentials (MEPs) .…”

Evaluation of a CL‐20/TATB Energetic Co‐crystal

“…2,4,6,8,10,12-Hexanitrohexaazaisowurtzitane, a polycyclic nitramine, commonly referred to as CL-20, is often found in these energetic-energetic co-crystals. CL-20 is currently the most powerful commercially available explosive, making it a major focus of cocrystallization efforts [1,[3][4][5][6][7][8][9][10][11][12][13][14][15]. CL-20 is of great interest for applications ranging from explosives to propellants; however, it is limited by its mechanical and thermal sensitivity to detonation [1,4,16].…”