Theoretical Study on the Effect of Solvent Behavior on Ammonium Dinitramide (ADN)/1,4,7,10,13,16‐Hexaoxacyclooctadecane (18‐Crown‐6) Cocrystal Growth Morphology at Different Temperatures

Abstract

The cocrystal of ammonium dinitramide (ADN)/1,4,7,10,13,16‐hexaoxacyclooctadecane (18‐Crown‐6) has effectively reduced the hygroscopicity of ADN. In order to understand the effect of solvent on the crystal growth, the interfacial models of ADN/18‐Crown‐6–ethanol are built and simulated by the molecular dynamics (MD) method at different temperatures (293–323 K, 10 K intervals). The energy, mass density, radial distribution function, and diffusion capacity of solvent are analyzed. The modified attachment energy (MAE) model is employed to study the solvent effect on cocrystal morphology. Results of MD simulation show that ADN/18‐Crown‐6 cocrystal has four important growth surfaces in vacuum, i.e., (2 0 0), (0 0 2), (1 1 0), and (2 0 −2). The binding energy of cocrystal and the absorbed energy of cocrystal–solvent are larger at 293 K than other temperatures. Hydrogen bonding interactions are formed between ADN/18‐Crown‐6 and solvent. More ethanol molecules adsorb on the crystal surface at lower temperatures, and hence the interaction between cocrystal and solvent is stronger. The morphology of ADN/18‐Crown‐6 cocrystal is different at various temperatures. The predicted morphology at 303 K is consistent with experimental shape. Moreover, cocrystal morphology at 293 K is a sphere‐like shape, which may reduce the hygroscopicity of ADN/18‐Crown‐6 cocrystal.