A design aid for crystal growth engineering

With the highly competitive development of chemical and pharmaceutical industries, mastering crystal growth is becoming increasingly necessary. Modern industrial manufacturers place high importance on the ability to grow crystals with a specific habit using tailored operating conditions. A detailed understanding of crystal growth is, therefore, vital for researchers in crystallography and crystallization to respond and realize this objective. Various models to predict crystal shape in the literature are reviewed here. The most commonly adopted are usually non-mechanistic and limited in their predictive power and utility, especially for products of industrial interest. Mechanistic models offer far more potential for rational crystal design, but require significant expertise to use and each new system studied typically requires additional investment. In this context, an automated implementation of mechanistic models (simulating and visualizing crystal growth under different environmental parameters) could eliminate this barrier to entry and promote widespread adoption to propel design of crystalline-based products into the next generation. With this need in mind, we have developed prototype software named ADDICT (Advanced Design and Development of Industrial Crystallization Technology), that enables an established spiral growth model to be applied to general systems of industrial interest. This proof-of-concept software provides an advanced theoretical framework to account for the solid state physics and surface chemistry, to guide experiments in a more efficient search of the design space for conditions that confer optimum functionality to the product. ADDICT calculates relative growth rates of crystal faces under the spiral regime, grown from vapor or solution, using information on the solid-state interactions that are organized into periodic bond chains. Solvent effects are principally accounted for by an interfacial modification of surface energies and the evolution of crystal habit under cycles of growth or dissolution can be predicted also. ADDICT has been tested for a variety of organic molecules, both centrosymmetric and non-centrosymmetric, resulting in successful predictions (examples for naphthalene, anthracene, paracetamol, lovastatin, D-mannitol, and α-glycine are presented).