Survey of Monte Carlo simulations of crystal surfaces and crystal growth

A Digital Mechanistic Workflow for Predicting Solvent-Mediated Crystal Morphology: The α and β Forms of l-Glutamic Acid

The solvent-mediated crystal morphologies of the α and β polymorphic forms of l-glutamic acid are presented. This work applies a digital mechanistically based workflow that encompasses calculation of the crystal lattice energy and its constituent intermolecular synthons, their interaction energies, and their key role in understanding and predicting crystal morphology as well as assessing the surface chemistry, topology, and solvent binding on crystal habit growth surfaces. Through a comparison between the contrasting morphologies of the conformational polymorphs of l-glutamic acid, this approach highlights how the interfacial chemistry of organic crystalline materials and their inherent anisotropic interactions with their solvation environments direct their crystal habit with potential impact on their further downstream processing behavior.

A temperature-controlled single-crystal growth cell for the in situ measurement and analysis of face-specific growth rates

The design and construction of a growth cell for the precision measurement of face-specific single-crystal growth rates are presented. Accurate mechanical drawings in SolidWorks of the cell and individual components are provided, together with relevant construction models. A general methodology for its use in the measurement of single-crystal growth rates and their underpinning growth mechanism is presented and illustrated with representative data provided for the crystal growth of the {011} and {001} faces of RS-ibuprofen single crystals grown in ethanolic solutions. Analysis of these data highlights the utility of the methodology in morphological model development and crystallization process design.

Precision measurement of the growth rate and mechanism of ibuprofen {001} and {011} as a function of crystallization environment

The growth rates of the {001} and {011} crystal faces of ibuprofen were measured as a function of the solution crystallisation environment from which the likely interfacial kinetic growth mechanisms were characterised.

Temporal coarse-graining of microscopic-lattice kinetic Monte Carlo simulations via tau leaping

A coarse-time-step method is presented that enables the execution of multiple events at each time increment of microscopic-lattice kinetic Monte Carlo simulations. The method employs the n-fold method to create groups of reactions in which the tau-leap algorithm of Gillespie, originally proposed for well-mixed systems, is applied. Creation of groups of reactions is an essential step to avoid violation of the leap condition that arises when the tau-leap algorithm is applied to a single site. The method is general, very easy to implement, and can result in substantial computational savings when global updating is employed. An illustrative example from crystal growth of a simple cubic lattice with the solid-on-solid approximation is presented.

Noninvasive in situ observation of the crystallization kinetics of biological macromolecules by confocal laser scanning microscopy

High-resolution confocal laser scanning microscopy (CLSM) is a powerful tool for in situ observation and analysis of protein crystal growth kinetics. Because the resolution of CLSM is not diffraction-limited by the object, it is possible to visualize, under certain conditions, objects in molecular dimensions. A modified batch technique is applied which allows the growth kinetics of sufficiently small crystallites fixed at the lower side of a cover glass, within a hanging drop, to be studied in reflected light near the total reflection angle. A gap, or cavity, filled with solution is formed between the cover glass and the upper crystal face, which acts to fix small crystallites by hydrodynamic friction forces. The cavity height enables the propagation of molecular steps across the upper crystal face without constraint, so that the propagation velocity and geometrical parameters can be measured by CLSM. The layer growth kinetics of monoclinic crystallites of a long-acting insulin derivative (Insulin Glargine) is investigated. For a twofold supersaturation of the solution, the growth is governed by 2D nucleation at the edges of the crystallites followed by a spreading of molecular steps. The layer growth kinetics are well fitted by the simple cubic kinetic lattice model. We find that only about one of a thousand solute (protein) molecules which push a kink place due to their Brownian motion becomes really incorporated into the growing crystal.