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O: Oberflächenphysik
O 29: Adsorption an Oberfl
ächen (III)
O 29.7: Vortrag
Donnerstag, 14. März 2002, 12:45–13:00, H43
Hydrogen Adsorption on Si(001): a Quantum Monte Carlo study — •Peter Kratzer3, Sorcha Healy1, Claudia Filippi2, Eckhard Pehlke4, Evgeni Penev3, and Matthias Scheffler3 — 1National University of Ireland, Cork, Ireland — 2Instituut Lorentz, Universiteit Leiden, The Netherlands — 3Fritz-Haber-Institut der MPG, Berlin — 4Universität GH Essen
The technologically important Si(001) surface has become a paradigmatic system to check our theoretical understanding of surface physics and chemistry. Notwithstanding the huge available data about this surface, fundamental aspects both of the clean surface and of its reactivity with H2 molecules are still subject to debate: Density-functional theory calculations of the energetics using a (semi-)local description of exchange and correlation (LDA,GGAs) were found in conflict with quantum chemical calculations using the configuration interaction (CI) method. We revisit the topics of clean surface buckling and H2 adsorption, employing cluster models of the surface in conjunction with an accurate treatment of electronic exchange and correlation effects within the quantum Monte Carlo (QMC) method. For the clean surface, the buckled ground state is confirmed by QMC, albeit with a smaller energy gain than in DFT. For the H2/Si(001) reaction, QMC calculations predict reaction energies and barriers significantly higher than LDA and most popular GGA functionals, but in good agreement with CI results where available. The higher adsorption barriers found in QMC are in better agreement than previous DFT results with the observed low sticking coefficient of H2 on Si(001). Various pathways for H2 desorption will be discussed as well.