A molecular dynamics simulation of solvent effects on the crystal morphology of HMX

Abstract

The solvent has a large effect on the crystal morphology of the organic explosive compound octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX, C 4H 8N 8O 8). The attachment energy calculations predict a growth morphology in vacuum dominated by (0 2 0), (0 1 1), ( 1 0 2 ¯ ) , ( 1 1 1 ¯ ) and (1 0 0) crystal forms. Molecular dynamics simulations are performed for these crystal faces of HMX in contact with acetone solvent. A corrected attachment energy model, accounting for the surface chemistry and the associated topography (step structure) of the habit crystal plane, is applied to predict the morphological importance of a crystal surface in solvent. From the solvent-effected attachment energy calculations it follows that the (1 0 0) face becomes morphologically more important compared with that in vacuum, while the (0 2 0) and ( 1 0 2 ¯ ) are not visible at all. This agrees well with the observed experimental HMX morphology grown from the acetone solution.