Regensburg 2019 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 8: Metal Substrates I: Adsorption and Reactivity
O 8.3: Vortrag
Montag, 1. April 2019, 11:00–11:15, H25
Oxidation of Transition-Metal Surfaces at Realistic Temperature and Pressure Conditions — •Zhong-Kang Han1, Ray Miyazaki2, Somayeh Faraji1, Santiago Rigamoni3, Maria Troppenz3, Claudia Draxl3,1, Jun-ya Hasegawa2, Sergey V. Levchenko4,1,5, and Matthias Scheffler1 — 1Fritz-Haber-Institut der MPG, Berlin, DE — 2Hokkaido University, Sapporo, JP — 3Humboldt–Universität zu Berlin, Berlin, DE — 4Skolkovo Innovation Center, Moscow, RU — 5NUST MISIS, Moscow, RU
Oxidation of metal surfaces is a ubiquitous phenomenon, but its thermodynamics is still not fully understood. Using the all-electron FHI-aims code, we perform a systematic DFT study (comparing various xc approximations) for the adsorption of atomic oxygen at (111) and (110) surfaces of Au, Pt, Ni, Pd and Cu, and the Pd- or Pt-alloyed Cu(111) and (110) surfaces. The finite-temperature thermodynamics is evaluated using a cluster expansion. At low coverages (<25%) O atoms are predicted to adsorb randomly at the short-bridge sites of elemental metal (110) surfaces, and they form a c(2× 2) pattern when the coverage increases, until a new c(2×√2) pattern forms with top and hollow sites occupied. Quite differently, at (111) surfaces a variety of ordered adsorbed O phases is found, with a mixed occupation of the fcc and hcp hollow sites. The structures of adsorbed O at the alloyed surfaces exhibit a larger variety of patterns depending on coverage, with Pd/Pt segregating to the surface at low O chemical potentials (i.e., higher temperatures and/or lower O2 pressures), while increasing the chemical potential induces Cu segregation.