Crystal Morphology Prediction of Hexahydro-1,3,5-trinitro-1,3,5-triazine by the Spiral Growth Model

Abstract

The crystal morphology of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) was predicted by the advanced Burton–Cabrera–Frank (BCF) model with consideration of non-centrosymmetric growth units. The present modeling showed that the advanced BCF model provides reliable results and understanding of the growth habit of RDX crystals grown from acetone and γ-butyrolactone, in which the {210} and {111} faces are dominantly developed. In the present work, the kink rate, which is the net flux input and output from kink sites along the edge, is found to be a critical factor for the crystal growth of RDX, where the energy required for detaching the growth unit from a kink site determines the existence probability of a growth unit. The {210} and {111} faces were found to show slow kink rates originated from the kink sites with a low existence probability and consequently became morphologically important faces. Moreover, the effect of solvent on the crystal growth habit of RDX, the difference in morphology of RDX grown f...