Investigation of the co-solvent effect on the crystal morphology of β-HMX using molecular dynamics simulations

In an attempt to explain the co-solvent effect on the shape of β-HMX crystals, molecular dynamics simulations were applied to systematically investigate the interactions of β-HMX crystal faces and the co-solvents (acetone/γ-butyrolactone, dimethylformamide/H₂O) by varying the volume ratio from 1: 3 to 3: 1. The growth habit of β-HMX in co-solvent was predicted using the modified attachment energy model. The results indicated that the (020) face of the β-HMX crystal has the weakest interaction with solvent molecule, and the binary solvent effects on different crystal faces varied such that the crystal morphology was affected significantly. The comparison of the β-HMX crystal aspect ratios grown from co-solvents with different volume ratios revealed that dimethylformamide/H₂O with volume ratio of 1 : 3 favors the spheroidization of β-HMX.