Morphology prediction of dihydroxylammonium 5,5′-bistetrazole-1,1′-diolate (TKX-50) crystal in different solvent systems using modified attachment energy model

In order to theoretically study the growth morphology of dihydroxylammonium 5,5′-bistetrazole-1,1′-diolate (TKX-50) crystal in different solvent systems, crystal–solvent models were established, and then molecular dynamics (MD) methods were adopted as a means to simulate particle motion. Modified attachment energy (MAE) model was employed to calculate the growth morphology of TKX-50. The simulation results demonstrate that COMPASS force field and RESP charge are suitable for molecular dynamics simulation of TKX-50. The morphologically dominant growth surfaces of TKX-50 in vacuum are (0 2 0), (0 1 1), (1 1 –1), (1 0 0) and (1 2 0), respectively. In water (H₂O) and N, N-dimethylformamide (DMF) solvents, the (1 1 –1) face is the largest in the habit face, the growth rate of (0 2 0) face becomes faster. With the increase of temperature, the aspect ratios of TKX-50 crystal in DMF solvent increase, and the areas of the (1 2 0) faces decrease. In ethylene glycol /H₂O mixed solvent system with volume ratio of 1/1, aspect ratio of TKX-50 is relatively small. In formic acid /H₂O mixed solvents with different volume ratios (1/4, 1/3, 1/2, 1/1 and 2/1), aspect ratio of TKX-50 is relatively small when volume ratio is 1/2.