Growth morphology of α-glycine crystals in solution environments: an extended interface structure analysis

• Published in: CrystEngComm 2010-01, Vol.12 (6), p.174-1749
• Main Authors: Gnanasambandam, Sivashangari, Rajagopalan, Raj
• Format: Article
• Language: English
• ISSN: 1466-8033; 1466-8033
• DOI: 10.1039/b922780f

Prediction of the morphology of organic crystals is a key first step in controlling crystal growth in chemical and pharmaceutical industries. Here, we predict the growth morphology and the relative growth rate of the morphologically important (010) and (011) faces of glycine crystals in aqueous solutions by fully accounting for the effects of solvent. Molecular dynamics simulations were used to obtain the relevant solvent-dependent properties such as the concentration of adsorbed growth units on the (010) and (011) faces and the amount of adsorbed growth units relative to the solute in the solution and are used along with molecular level crystallographic properties such as interplanar distance and crystallographic factor in newly developed "extended interface structure analysis" to determine the relative growth rates and morphology. We observe that the growth rate of the (011) face is 2.88 times greater than that of (010) face, consistent with experimental observations, in contrast to the much higher relative growth rates (4 to 7) predicted by attachment energy calculations in the literature in the absence of solvent. We show that the polar group present on the (011) face has stronger interactions with the solvent and reduces the growth rate, thereby underscoring the importance of the need to incorporate solvent effects in crystal growth analysis. Our prediction of the growth morphology is also consistent with experimental observations. Overall, the approach presented paves the way for exploring the effects of other solvents and impurities on the kinetics and the morphology of crystal growth. A first-principle, computational method is developed to incorporate the effects of solvents on crystal morphology. Predictions for α-glycine from aqueous solutions are in excellent agreement with experiments.