Berlin 2018 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 118: Metal substrates: Structure, epitaxy and growth

O 118.3: Vortrag

Freitag, 16. März 2018, 11:30–11:45, MA 005

(Meta)-stability of bimetallic surfaces: A computational study — •David Mahlberg and Axel Gross — Institut für Theoretische Chemie, Universität Ulm, 89069 Ulm, Germany

The catalytic properties of bimetallic surfaces sensitively depend on their composition and/or structural arrangement. However, it is often not clear how stable these structures are under reaction conditions such as high temperatures. Here we present first principles-based kinetic Monte-Carlo (kMC) simulations to analyze the (meta-)stability of PtRu/Ru(0001) surface alloys.

Typically structural changes in metals occur via vacancy diffusion. In a first step, the enthalpy of vacancy formation was determined by density functional theory calculations. There is a high energetic cost of their formation, resulting in a small concentration of vacancies on the surface, in agreement with scanning tunneling microscope (STM) results [1]. In a second step, barriers for vacancy diffusion were derived as a function of the surrounding composition of bimetallic surface alloy which then enter the kMC simulations as jump rates derived via transition state theory. We will present results of the time evolution of the structure of PtRu/Ru(0001) surface alloys and analyze them in terms of the interaction between the constituents of the bimetallic surface.

[1] H. E. Hoster, A. Bergbreiter, P. M. Erne, T. Hager, H. Rauscher and R. J. Behm, Phys. Chem. Chem. Phys. 10, 3812 (2008).