Séminaire/Seminar - Crystal Nucleation: the birth of order from disorder - Alexander E.S. Van Driessche

Monday April 24th at 11AM

INSP - Sorbonne Université - 4 place Jussieu - 75005 Paris - Barre 22-23, 3^e étage, salle 317

Alexander E.S. Van Driessche (Universidad de Granada, Spain)

Nucleation of crystals is the process of forming a small, organized structure(called a nucleus) within a disordered environment. This small structure then acts as a seed for the growth of a larger, more organized structure. Until recently, it was assumed that the formation of these crystal seeds was a one step process, with the initially formed microscopic nuclei displaying similar properties (e.g. structure, density) as the final macroscopic phase. This is described by classical nucleation theory [1]. However, during the past decade we have acquired the ability to observe the birth of crystals from up close with unprecedented temporal and spatial resolution. These observations have revealed that during the early stages of crystallization many systems do not adhere to our classical image of forming an initially ordered crystal seed, instead the system transitions through different states of (partial) disordered states before attaining a final order crystal structure [2]. These pathways involving precursor and/or intermediate phases are commonly referred to as nonclassical nucleation. (Non)classical nucleation is as a key event in many fields of science and engineering and lies at the core of many biomineralization processes. In the latter, organisms often exert a tight control over the initial stages of crystallization (using e.g. proteins) to create intricate structures and/or to promote the formation of metastable phases. The explain many of these observations we need to rely on nonclassical nucleation models. In addition, a thorough understanding of the nonclassical pathways of industrially relevant materials (e.g. cement phases) is also paramount to develop new sustainable materials with improved properties. During this talk I will present an overview of the different nucleation models. Special emphasis will be placed on the role nonclassical nucleation plays in the transition from disorder to order and how this is changing our understanding of crystal structure and its properties. Finally, I will briefly review some old and new concepts of how organic molecules control nucleation at the nanoscale.

[1] D. Kashchiev, Nucleation: Basic Theory with Applications, Butterworth-Heinemann, Oxford, 2000.

[2] A.E.S. Van Driessche, M. Kellermeier, L. G. Benning, D. Gebauer, NewPerspectives on Mineral Nucleation and Growth: from Solution Precursors to SolidMaterials, ed., Springer International Publishing, Cham, 2017.