Regensburg 2004 – wissenschaftliches Programm
O 38.8: Vortrag
Donnerstag, 11. März 2004, 17:30–17:45, H38
Stability of Pd Surface Oxides at Ambient Pressures — •M. Todorova1, J. Rogal1, K. Reuter1, M. Scheffler1, E. Lundgren2, J. Gustafson2, J.N. Andersen2, and A. Stierle3 — 1Fritz-Haber-Institut, Berlin — 2Departement of Synchrotron Radiation Research, University of Lund, Sweden — 3Max-Planck-Institut für Metallforschung, Stuttgart
Using density-functional theory we study and compare the oxide formation at the Pd(111) and Pd(100) surfaces. We identify the stable phases and determine their (T,p) stability range using the concept of first-principles atomistic thermodynamics. The observed surface oxides, which only vaguely resemble their bulk counterparts, represent the most stable phase for a wide range of environmental conditions exceeding the stability range of bulk PdO by far. The corresponding overall structure of the surface phase diagram for the Pd(100) surface is in good agreement with surface X-ray diffraction (SXRD) measurements in the pressure range up to 1 bar. For T < 600K the comparison with the experimental data additionally discerns a kinetic hindrance to the formation of the bulk oxide, stabilizing the (√5 × √5)R27∘ surface oxide even up to ambient pressures.