Berlin 2018 – scientific programme
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O: Fachverband Oberflächenphysik
O 73: Surface dynamics: Reactions, elementary processes and phase transitions II
O 73.5: Talk
Wednesday, March 14, 2018, 17:45–18:00, MA 043
Phase Diagrams of Titanium Clusters in a Reactive Oxygen Atmosphere:a Replica-Exchange Grand-Canonical ab initio Molecular-Dynamics study — •yuanyuan zhou, matthias scheffler, and luca m. ghiringhelli — Fritz-Haber-Institut der Max-Planck-Gesellschaft
TiO2 has widespread applications such as photocatalysis, photovoltaics, and oxide electronics. To help elucidate the microscopic details of the catalytic processes, experimental and theoretical works have been performed on titanium-oxide clusters in the past decade (e.g., S. Bhattacharya et al., PRB 91, 241115 (2015)). Here, the replica-exchange (RE) grand-canonical (GC) molecular-dynamics method, recently developed by us, is used to explore Ti4/8 cluster in contact with a reacting atmosphere of O2 molecules. The method enables the unbiased, efficient calculation of complete p − T phase diagrams. The system is modeled via DFT, at the PBE level. The GC ensemble is adopted to describe clusters in a reactive atmosphere. RE allows for an efficient sampling by shuttling configurations from regions of low T or high chemical potential (µ) to regions of high T or low µ. This massively parallel method requires no prior knowledge of the phase diagram and takes only the potential energy function together with the desired µ and T ranges as inputs. We identify the thermodynamically most stable phases of Ti4/8Ox at realistic T/pO2 conditions, as a first step towards an understanding of the complex titanium-oxide surfaces at the atomistic level.