Prediction of morphology of CL-20/TFAZ cocrystal crystals in binary solvents based on modified attachment energy model

Abstract

Crystal morphology of CL-20/TFAZ cocrystal in vacuum was predicted using the attachment energy (AE) model. Additionally, the modified attachment energy (MAE) model and molecular dynamics (MD) method were utilized to predict the crystal morphology of CL-20/TFAZ cocrystal in four different binary solvents, namely, isopropyl alcohol (IPA)/acetone (AC), IPA/dimethyl sulfoxide (DMSO), IPA/ethyl acetate (EA), and IPA/water (H2O). The radial distribution function (RDF) between the solvent and crystal surface and the mean square displacement (MSD) of the solvent were calculated. The findings showed that the morphology of CL-20/TFAZ cocrystal in vacuum was an irregular polyhedron with eleven important growth surfaces: (001), (1−10), (110), (100), (011), (0−11), (10−1), (020), (0−20), (11−1), and (1−1−1), with the (001) surface having the highest area ratio of 31.693 %. The crystalline morphology in IPA/AC, IPA/DMSO, and IPA/EA solvents was block-shaped, while it was rod-shaped in IPA/H2O. Comparing the RDF values of the four solvents, IPA/H2O exhibited the largest g(r) value and could more easily adsorb onto the crystal surface of CL-20/TFAZ cocrystal. Interestingly, IPA/H2O solvent had the smallest MSD value, suggesting the slowest diffusion rate, while IPA/AC solvent exhibited the fastest diffusion rate. Overall, IPA/EA solvents were more suitable for the formation of CL-20/TFAZ cocrystal.