Berlin 2018 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 52: Methods in Computational Materials Modelling (methodological aspects, numerics)

MM 52.1: Talk

Thursday, March 15, 2018, 10:15–10:30, TC 006

Finding reaction coordinates for crystal nucleation in Ni — •Grisell Diaz Leines, Ralf Drautz, and Jutta Rogal — Ruhr- Universität Bochum, Universitätsstrasse 150, 44801 Bochum, Germany

Despite the technological importance of crystal nucleation, fundamental insight into the early stages of solidification is often hampered by the long timescales and complexity of the process. In this work we employ transition path sampling simulations together with a maximum likelihood analysis of the committor function to identify the reaction coordinates that best describe the nucleation mechanism in nickel. The analysis of the reweighted path ensemble on a set of candidate structural order parameters shows that the nucleation pathway in Ni is governed by the initial formation of mesocrystal regions and a subsequent emergence of fcc-hcp crystallites embedded within the core of these prestructured clusters. Our findings indicate that the prestructured liquid cloud is an order parameter that enhances the reaction coordinate and therefore has an essential role in the structural description of the nucleus and its interfacial free energy. Moreover, we show that the prestructured regions predetermine the coordination of the fcc-hcp polymorphs selected, acting as precursors of the crystallization. These results shed light not just on the atomistic mechanism of nucleation during solidification in Ni but also on the process of polymorph selection.