Spheroidal crystal morphology of RDX in mixed solvent systems predicted by molecular dynamics

Abstract

The crystal morphology of RDX largely affects its stability, dispersion, and energy output. The influence of the solvent on the crystal morphology plays a key role. A molecular dynamics method is used to calculate the interaction energies between five important crystal planes of RDX and the solvent layer under the action of cyclohexanone/water and dimethyl sulfoxide/acetone mixed solvents. The attachment energies are modified and the crystal morphologies of RDX under the effect of different volume ratios of the mixed solvents are predicted. The results show that the five important crystal planes of RDX are attracted to the two mixed solvents. Compared with the (111) and (210) faces, the (200), (002), and (020) faces show more obvious growth phenomena under the action of the two mixed solvents. When the mixed solvent is cyclohexanone/water, the lower the proportion of cyclohexanone, the closer the RDX crystal morphology is to spherical. When the mixed solvent is dimethyl sulfoxide/acetone, if spheroidal RDX is desired, the proportion of acetone should be greater than or equal to the proportion of dimethyl sulfoxide. The radial distribution functions between O atoms of the (111) face and H atoms in the two mixed solvents under different volume ratios are analyzed to explore the interaction forces at the interfaces.