A Generalized Interfacial Structure Analysis Model for the Crystal Morphology: β HMX

We studied the spiral growth mechanism of β-cyclotetramethylenetetranitramine (β-HMX) crystals with (0 2 0), (0 1 1), (1 1 0), and (1 0 1) faces, both experimentally and theoretically. In this work, a generalized interfacial structure analysis model is suggested to elucidate the morphology of β-HMX. There are two significant factors on crystallization procedure; 1) Molecular concentration near the surface of crystal 2) Whether pre-ordering of growth units occur during adsorption on the surface of each crystal faces. We investigated these through the Molecular Dynamic approach and metadynamics simulation, respectively. However, due to high conformational free energy barrier, pre-ordering of the growth unit does not occur and the factor 1 plays critical role in crystal growth, so the result of present work indicates that anisotropic local concentration of the growth units at the interface is the main factor determining relative growth rates, which was consistent with those of previous studies.