Study on the effect of solvent on cocrystallization of CL-20 and HMX through theoretical calculations and experiments

Cocrystallization is a helpful method for explosives design. However, lack of understanding of the cocrystallization mechanism leads to inefficiency in cocrystal preparation. Therefore, studying the effects of solvent on cocrystal is of great importance for the efficient application of 2,4,6,8,10,12-hexanitrohexaazaisowurtzitane (CL-20). In this paper, the effect of solvent on cocrystallization is investigated by the CL-20/HMX cocrystal/solvent cluster model, the CL-20/HMX/solvent mixture model, the CL-20/HMX cocrystal/solvent interface model combined with quantum chemistry and molecular dynamic methods. The authors find that the hydrogen bond between CL-20 and 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX) is the strongest and the binding energy of cocrystal and solvent molecules is the weakest in ethyl acetate (EA) solvent, indicating that CL-20 and HMX tend to be combined together and there is less hindrance by solvent molecules. Analysis of the CL-20/HMX/solvent mixture and mass density distribution studies show that the solvent effect has a great influence on the crystal faces and the cocrystallization rate of CL-20 and HMX is the highest in EA solvent. The XRD and SEM characterization results are consistent with the theoretical calculations. The present work on the effects of solvent on CL-20/HMX cocrystals is beneficial for understanding the mechanism of the growth of energetic cocrystal materials. It is helpful in selecting more suitable theoretical and experimental conditions and makes access to excellent cocrystals more efficient.