Theoretical Study On The Solvated Growth And Morphology Control Of TKX-50

Dihydroxylammonium 5,5?-bistetrazole-1,1?-diolate?TKX-50?is a kind of promising energetic ionic salt which shows higher detonation velocity and lower mechanical sensitivities.In order to explain the influence of solvent on the crystal morphology of TKX-50,the properties of TKX-50 molecule in different solvent models and the effects of different solvents on the crystal morphology of TKX-50 were studied from the perspective of theoretical calculation.The difference on the crystal morphology of TKX-50 in solvents predicted by different theoretical models was compared,so as to screen the solvents suitable for TKX-50 crystallization and provide a reference for the development of low-sensitivity TKX-50.The solvation effect of TKX-50 in six solvents was studied using density functional theory and SMD solvation model.The studies show that the solvent effect has a greater influence on the N-O bond length and the dihedral angle formed around the C-C bond in the TKX-50 molecular structure.The negative charges are mainly transferred to the N atoms of the TKX-50 molecular skeleton and the O atoms of the hydroxylammonium cation in solvent phase.Compared with the gas phase,TKX-50 has a increased band gap in the solvent phase.The distribution of electrons in the solvent phase is non-uniform.Compared to the gas phase,the localization of the electrons is reduced.The vacuum morphology of TKX-50 crystal was predicted by attachment energy model.The results show that PCFF force field is suitable for the study of TKX-50.The morphologically dominant growth surfaces of TKX-50 in vacuum are?0 2 0?,?1 0 0?,?0 1 1?,?1 1 0?,?1 1-1?and?1 2-1?,respectively,and the aspect ratio is 1.98.The?0 1 1?face has the strongest morphological importance,and the growth of?1 1-1?face is higher than those of other faces.?1 1 0?face has a rough topography and?1 0 0?face is the flattest by analyzing the properties of crystal surface.The modify attachment energy model 1?known as MAE1?was used to calculate the relative growth rates of TKX-50 crystal faces in six solvents and FA/H₂O mixed solvents with different volume ratios,so the crystal morphologies of TKX-50 in the solvents were predicted.The analysis of radial distribution function shows that the main interactions between TKX-50crystal faces and solvent molecules are hydrogen bonding,van der Waals and electrostatic interactions.The form of hydrogen bonding is O-H···O,which is a strong hydrogen bond.The morphology prediction and aspect ratio calculation results show that EG and DMF solvents are more conducive to the spheroidization of TKX-50 in a monolithic solvent system.In the FA/H₂O mixed solvent system,the volume ratio of 1/2 is favorable for the spheroidization of TKX-50.The modify attachment energy model 2?known as MAE2?and occupancy model were used to predict the crystal morphologies of TKX-50 in EG and DMF solvents,and compared with the experimental results.The morphologies of TKX-50 in solvents predicted by MAE2and occupancy models are basically similar.The MAE1 method is a special case of the MAE2method,and the MAE2 method is more general and more applicable.In addition,if the role of solute molecules in solution is considered,the occupancy model is more applicable than the MAE1 and MAE2 methods.