Berlin 2005 – wissenschaftliches Programm
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O: Oberflächenphysik
O 18: Adsorption an Oberfl
ächen II
O 18.5: Vortrag
Samstag, 5. März 2005, 11:45–12:00, TU EB301
Analyzing the order-disorder transition in hydrogen adsorption on Pd(111) with a first-principles lattice gas hamiltonian approach — •Cesar Lazo1, Karsten Reuter2, Volker Blum2, Frerich Keil1, and Matthias Scheffler2 — 1TU Hamburg-Harburg, Eissendorfer Str. 38, D-21071 Hamburg — 2Fritz-Haber-Institut, Faradayweg 4-6, D-14195 Berlin
The interaction of hydrogen with Pd surfaces is of particular interest in many industrial reactions, including hydrogenation and fuel cell technologies. We set out to study the mesoscopic ordering behavior of hydrogen on Pd(111) from first-principles by parametrizing a lattice gas Hamiltonian (LGH) with density-functional theory (DFT) data. The subtle energy differences involved in the hydrogen bonding make this a critical test case, and we discuss the present methodological limitations with respect to basis set, exchange-correlation functional, and LGH expansion. Using our LGH model we then carry out Monte Carlo simulations in order to obtain the (T,p)-phase diagram, as well as the configurational energy density of states (DOS) using the Wang-Landau algorithm. With this DOS we calculate the configurational entropy and can correlate it with the experimentally observed low critical temperatures for the order-disorder transition in the H/Pd(111) system.