Dresden 2017 – scientific programme
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O: Fachverband Oberflächenphysik
O 101: Heterogeneous Catalysis: Theory I
O 101.5: Talk
Thursday, March 23, 2017, 18:15–18:30, TRE Phy
Complex Reaction Networks of Oxygen Activation on Ag Clusters with Multi-Spin States at Finite Temperature — •Weiqi Wang, Matthias Scheffler, and Luca M. Ghiringhelli — Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin
To understand the process of the oxygen activation on (noble) metal clusters such as Ag4, Ag8, it is critical to take finite temperature effects into account. Transient structures, having their spin ground states different from those of stable structures, could be crucial in promoting the activation of oxygen. The appearance of those transient structures, however, introduces extra complexity into the reaction network. In this work, the reaction network of oxygen adsorption on silver clusters are studied at finite-temperature and different spin states. By estimating the transition matrices, the Markov state models (MSM) are established, based on the trajectories at parallel temperatures obtained from replica-exchange (first-principles) molecular dynamics (REMD). Reaction pathways are then analyzed by transition-path theory (TPT) based on the converged sampling on MSM. The MSMs and the reaction pathways are embedded in 2-dimensions by using the non-linear dimensionality reduction method Sketch-Map. In addition, 2-dimensional free energy plots are also calculated by the Boltzmann-reweighting method multi-state Bennet acceptance ratio (MBAR). We show that the adsorption and activation of oxygen benefits from the transient geometries, with spin states different from the ground state, that are available at finite temperature. This work was supported by the UNICAT cluster of excellence (DFG).