Berlin 2018 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 37: Microstructure and Phase Transformations

MM 37.5: Talk

Wednesday, March 14, 2018, 12:45–13:00, TC 010

Dynamics of sub-nm Pt clusters on carbon-based materials: Computation meets STEM measurements — Marta Bon, Trond Henninen, Daniele Passerone, and •Rolf Erni — Empa Swiss Federal Laboratories for Materials Science and Technology, Switzerland

Crystallization, condensation and precipitation from a solution are three different phase transitions which are commonly described by the classical nucleation theory (CNT). CNT is generally in agreement with experiments, however does not define what fundamentally constitutes a pre-nucleation state or how a nucleus is formed at all. State-of-the-art scanning transmission electron microscopy (STEM) allows observing the dynamics of clusters smaller than 2 nm in size at atomic resolution.[1] Being however 2D projections of the 3D geometry of the clusters, STEM images are challenging to interpret directly. Molecular dynamics simulations boosted by enhanced sampling techniques, such as metadynamics,[2] can complement the high-resolution STEM measurements, and shed light on the formation, dynamics, stability, and evolution of tiniest atomic clusters which represent the embryos of solid matter. We show, in particular, the Pt 3D structures deposited on carbon-based materials, explaining how temperature and the interactions between the Pt atoms and the substrate can affect the clustering process.

[1] T. J. Woehl, et al. ACS Nano 6.10 (2012): 8599-8610. [2] A. Barducci, G. Bussi, and M. Parrinello. Phys. Rev. Lett. 100.2 (2008): 020603.