9. IKZ - Sommerschule Kristallzüchtung 2016

     

"Towards understanding crystal growth at the atomic-scale"

Lecturer: Elias Vlieg, Radboud University, Institute for Molecules and Materials, Nijmegen, The Netherlands

October 12-14, 2016

    With the following four lectures
      Wednesday, October 12, 2016, 10:00 - 12:00
        Morphology prediction
      Wednesday, October 12, 2016, 14:00 - 16:00
        Role of surface and interface structure during crystal growth
      Thursday, October 13, 2016, 10:00 - 12:00
        Growing better protein crystals without convection
      Friday, October 14, 2016, 10:00 - 12:00
        Crystallisation routes to single chirality
    The growth of crystals, whether this is a large and highly-perfect silicon boule or powder-like material of an active pharmaceutical ingredient, always takes place at the interface with its growth medium and (nearly) always atom by atom (or molecule by molecule). A complete understanding of crystal growth, and a subsequent control of the crystal properties, therefore requires an atomic-scale knowledge of the processes and structure at the interface. This series of lectures describes attempts to understand several topics from this atomic-scale perspective.
    The faceted nature of a crystal (like quartz) makes anyone curious about the origin of this shape and understanding and predicting the morphology (habit) of a crystal is therefore a very classic subject. Both old and new models for this will be discussed.
    At the growth interface, both the crystal and the growth medium will typically have a structure that is different from the bulk. Assessing such interfaces, in particular when growing from a solution or melt, is quite difficult, but a combination of techniques like Atomic Force Microscopy, computer simulations and X-ray diffraction, has yielded significant insights. A number of examples will be discussed, including the ordering of Ga at the GaN-Ga interface at high pressure and temperature as observed using high-energy X-rays from synchrotron radiation sources.
    In many applications one aims to grow highly perfect crystals. In the case of protein crystals, the perfection is needed to achieve a high resolution of the protein structure. Growth without convection has several advantages in this context and a number of routes to achieve convection-free growth will be discussed. The resulting slow growth leads to better crystals and to a reduced uptake of impurities. This thus also yields lessons for the growth of other types of crystals.
    Nature is homochiral; for example nearly all natural amino acids are left-handed. This not only raises the fundamental question of why nature made this particular choice, but also has practical consequences for pharmaceutical ingredients, because the left-handed version can have very different effects than the right-handed one. Crystallisation is one route to obtain chirally pure material. In the last decade a number of new and surprising routes have been found. In Viedma ripening, for example, grinding a slurry of left- and right-handed crystals leads to a complete conversion of all the solid material to single chirality. This process involves interesting growth routes in which growth appears to take place by the incorporation of small clusters.
    Elias Vlieg is professor in Solid State Chemistry in the Institute for Molecules and Materials (IMM) of the Radboud University in Nijmegen, The Netherlands. The research theme of his group is the fundamental understanding of crystal growth, for which a wide range of experimental, computational and theoretical methods are applied to a wide range of crystals. His current interests include chiral separation, additives, nucleation, polymorphism, self-assembly and the atomic-scale structure of solid-liquid interfaces. As head of the Applied Materials Science group, he is further involved in the practical applications of III-V semiconductors for thin film solar-cells, including a role as CEO of a small spin-off company.