Solvent effects on the crystal morphology of β-HMX studied by modified attachment energy and occupancy models

Abstract

The crystal habits of 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX) in acetone and DMSO/H2O solvent systems were separately investigated by the modified attachment energy (MAE) model and the occupancy model. The calculated results show that the (011) face and (110) faces have large morphological importance in both two solvents. Compared with that from the MAE model, the predicted morphologies from the occupancy model are in better agreement with the experimental results. Additionally, radial distribution function (RDF) analysis demonstrates that the weak hydrogen bond, vdW interactions and Coulomb interactions exist extensively between HMX and solvent molecules, among which the hydrogen bonds dominate the solvent-surface interactions. Noticeably, the strong hydrogen bonds formed between H atoms from solvents and O atoms from HMX were witnessed in the DMSO/H2O solvent, whose effect on the crystal morphology may be greater than that of weak hydrogen bonds and other interactions despite its relatively low intensity. The above results would deepen the understanding of the effect of different interactions at the interface on the growth morphology of energetic materials.