The step energy as a habit controlling factor: Application to the morphology prediction of aspartame, venlafaxine, and a yellow isoxazolone dye
Deij, M. A., Meekes, H., Vlieg, E.
CRYSTAL GROWTH & DESIGN 7 (10): 1949-1957 OCT 2007

Abstract: In this paper, we report on the use of step energies in crystal morphology prediction as an improvement and computationally fast alternative to the Bravais, Friedel, Donnay, and Harker (BFDH) and attachment energy methods. One of the major improvements is a morphology prediction that is dependent on the driving force for crystallization. Step energies are calculated using STEPLIFT, an automated procedure to find the lowest step energies of infinitely long and straight steps. These steps are constructed by a combination of the connected nets of two nonparallel flat faces (F-faces), one representing the step terraces, the other the step edge. Step energies obtained in all relevant directions on a specific crystal face are used for a two-dimensional (2D) Wulff construction. This leads to the equilibrium shape of a 2D nucleus having the lowest energy, which can be used as a classification for the nucleation barrier, for example, in 2D birth and spread growth. Using the 2D nucleus energy, a link between the atomistic description of the steps and the macroscopic growth morphology is made using crystal growth theory to calculate growth rates as a function of the driving force for crystallization. This procedure is applied successfully to predict the crystal morphology of aspartame II-A, venlafaxine, and two polymorphs of a yellow isoxazolone dye.