Regensburg 2019 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 32: Complex Fluids and Soft Matter (joint session DY/CPP)

DY 32.14: Talk

Wednesday, April 3, 2019, 18:45–19:00, H3

Gold nanoclusters at room temperature: are they soft matter? — •Luca M. Ghiringhelli, Bryan Goldsmith, Diego Guedes-Sobrinho, Jacob Florian, Jin-Xun Liu, Weiqi Wang, Juarez Da Silva, Ian Hamilton, and Matthias Scheffler — Fritz-Haber- Institut der Max-Planck-Gesellschaft, Berlin, Germany

Soft matter encompasses systems for which the predominant physical behaviors occur at an energy scale comparable with room-temperature (T=300 K) thermal energy. Here, we present a study of free-energy landscapes of neutral gold nanoclusters in the size ranges 10–13 (arXiv:1811.08062) and 25–40 (arXiv:1811.04438) atoms. Gold nanoclusters are interesting for their possible applications in gas sensing, pollution reduction, and catalysis. Our studies are based on extensive Born-Oppenheimer density-functional-theory replica-exchange molecular-dynamics sampling over a wide range of temperatures. We find that the long-standing question “At which size (neutral) gold clusters start favoring 3D vs 2D structures?” should be recast, at least in the size range between 10 and 13 atoms, into the question (here answered): “At which temperatures are 3D structures favored?”. At T=300 K, we find that the typical activation barrier of Au–Au bonds is indeed comparable with the thermal energy, resulting in a continuous reshuffling of bonds and, in the size range 25–40 atoms, in low free-energy structures that significantly differ from the T=0 K structures. In these examples, gold nanoclusters seem indeed to match the definition of soft matter. This might have important implications for the characterization of the chemical reactivity of these systems.