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O: Fachverband Oberflächenphysik
O 55: Oxide and insulator surfaces: Structure, epitaxy and growth II
O 55.5: Vortrag
Mittwoch, 11. März 2026, 11:45–12:00, HSZ/0204
Size Matters: Size-dependent non-equilibrium dynamics of fluxional subnanoclusters — •Patricia Poths1, King Chun Lai2, Christoph Scheurer1, Sebastian Matera1, and Karsten Reuter1 — 1Fritz-Haber-Institut der Max-Planck Gesselschaft, Berlin — 2Max Planck Computing and Data Facility, Garching
Sub-nanoclusters are known to be fluxional, thermally populating multiple structural isomers, and to have size-dependent catalytic behavior. Due to computational limitations, only quasi-static equilibrium properties could be addressed by first-principles methods so far. Here, we investigate the kinetic evolution underlying isomer fluxionality by coupling machine-learned interatomic potentials (MLIPs) with our recently introduced automatic process explorer (APE) [1]. With this methodology, we construct comprehensive isomerization networks of Pdn (n=3-11) clusters deposited on the MgO(100) surface, and evaluate the corresponding state-to-state dynamics. Using methods from Markov State Modeling, we find that the intrinsic timescales for equilibration can vary by several orders of magnitude based on cluster size. Furthermore, intrinsic timescales for each cluster isomer can vary by multiple orders of magnitude, indicating the existence of metastable sets with quasi-liquid behavior, i.e. rapid conversion between isomers within the set but only slow transition to isomers outside. These simulations reveal that the prevalent quasi-static picture is of limited use for nonequilibrium problems like catalysis, but also that relaxation dynamics should be observable on experimental timescales.
[1] K.C. Lai et al., Phys. Rev. Lett. 134, 096201 (2025).
Keywords: fluxionality; dynamics; restructuring