Crystal morphology of dihydroxylammonium 5,5′-bistetrazole-1,1′-diolate (TKX-50) under solvents system with different polarity using molecular dynamics

Dihydroxylammonium 5,5'-bistetrazole-1,1'-diolate (TKX-50) is a kind of promising energetic ionic salt which shows excellent properties including higher detonation velocity and lower mechanical sensitivities. In order to explain the influence of solvent on the morphology of TKX-50 crystal, the two-dimensional nucleation theory was used to modify the attachment energy (AE), molecular dynamics (MD) simulation was employed to investigate the interaction of TKX-50 and solvents. The results demonstrated that the morphologically dominant growth surfaces of TKX-50 in vacuum are (0 2 0), (1 0 0), (01 1), (1 1 0), (1 1 -1) and (1 2 -1), respectively. It had intramolecular and intermolecular hydrogen bonds with different strength in the TKX-50 crystal. The effect of solvent on the crystal plane was further explained through the analysis of radial distribution function (RDF) and mean square displacement (MSD). The morphologies of TKX-50 in solvents with different polarity were predicted, and an empirical correlation formula was fitted by comparing the aspect ratios (R) of the crystals, solvent polarity (P) and the root mean square values (I) of the solvent molecular diffusion coefficient. Results of comparing the TKX-50 crystal aspect ratios in different solvents indicated that the Ethylene Glycol (EG) solvent is more favorable for the spheroidization of TKX-50 in this study.