(304g) Simulating the Shape Evolution of Crystals with Monte Carlo Methods

Crystallization from a solution is an important process to produce particulate materials in industry. Often not only the size of the particulate products but also the specific shape of the crystals need to be tailored in order to meet the demands of the applications like pharmaceuticals, catalysis or electronics. From the molecular perspective the evolution of a crystal shape is influenced by several phenomena. Diffusion of the molecules or basic building blocks with several molecules transports the material needed to growth crystals from a starting nucleus. The attachment of these primary units on and into the crystal may be different at different crystal faces depending on the corresponding energy barrier to incorporate these units. After the attachment the units might still be able to change their position on the surfaces of the crystal. The incorporation at steps might be less favorable than the incorporation into holes of an already build surface. The dynamical picture of the shape evolution therefore will depend on a number of material and process conditions. Here we will present a Monte Carlo based method where the aforementioned phenomena are incorporated and different scenarios of a shape evolution of crystals from solution are presented. In experiments on barium sulfate we have seen very interesting crystal shapes of different kinds [1]. The simulation of such systems will provide a deeper insight into the shape evolution and will help to improve our understanding of the crystallization process as a whole. [1] C. Steyer and K. Sundmacher: Impact of feeding policy and ion excess on particle shape in semi-batch precipitation of barium sulfate, J of Crystal Growth (2009), doi:10.1016/j.jcrysgro.2009.02.046 .