Crystal morphology prediction of 1,3,3-trinitroazetidine in ethanol solvent by molecular dynamics simulation

•Crystal morphology of TNAZ in vacuum and solvent was predicted by attachment energy.•Crystal shape of TNAZ becomes more regular in ethanol solvent.•Interaction energies include hydrogen bond, coulomb and van der Waals forces.

In order to understand the mechanism of the effect of solvent on the crystal morphology of explosives, and be convenient for the choice of crystallization solvent, the attachment energy (AE) model was performed to predict the growth morphology and the main crystal faces of 1,3,3-trinitroazetidine (TNAZ) in vacuum. The molecular dynamics simulation was applied to investigate the interactions of TNAZ crystal faces and ethanol solvent, and the growth habit of TNAZ in ethanol solvent was predicted using the modified AE model. The results indicate that the morphology of TNAZ crystal in vacuum is dominated by the six faces of [0 2 1], [1 1 2], [0 0 2], [1 0 2], [1 1 1] and [0 2 0], and the crystal shape is similar to polyhedron. In ethanol solvent, The binding strength of ethanol with TNAZ faces changes in the order of [0 2 1] > [1 1 2] > [0 0 2] > [1 0 2] > [1 1 1] > [0 2 0], which causes that [1 1 1] and [0 2 0] faces disappear and the crystal morphology becomes more regular. The radial distribution function analysis shows that the interactions between solvent and crystal faces mainly consist of coulomb interaction, van der Waals force and hydrogen bonds.

Graphical abstractThe equilibrium configuration of ethanol adsorbing on (1 0 2) crystal face of TNAZ. The MD simulation result of ethanol interacting with TNAZ (1 0 2) face indicates that the solvent molecules have contacted closely with TNAZ face, including extensive interactions (hydrogen bonds, coulomb and van der Waals forces) between them. Consequently, the crystal faces must get rid of ethanol solvent molecules before they can grow. The process requires an expenditure of energy and the interactional energy increases with the binding strength. Therefore, the interaction reduces the growth rate of certain crystal faces. And finally the solvent modifies the crystal shape of TNAZ by its different interaction with different crystal faces.Figure optionsDownload full-size imageDownload high-quality image (98 K)Download as PowerPoint slide