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O: Fachverband Oberflächenphysik

O 51: Surface chemical reactions I

O 51.1: Vortrag

Donnerstag, 26. März 2009, 16:15–16:30, SCH A01

Ab initio molecular dynamics simulation of electronic energy dissipation: A comparison of H/Si(001), H/Al(111), and HCl/Al(111) — Georg Krugel, Michael Grotemeyer, Jan van Heys, Michael Lindenblatt, and •Eckhard Pehlke — Institut für Theoretische Physik und Astrophysik, Universität Kiel, Germany

The energy transfer to solid surfaces during chemisorption and surface scattering is of considerable relevance. Energy dissipation via electron-hole pair excitation has attracted much recent interest, see e.g. [1]. To identify the electronic dissipation mechanisms, we carry through ab initio molecular dynamics simulations. The time-dependent Kohn-Sham equations of the electrons are integrated numerically, while the positions of the ions follow from Ehrenfest dynamics. The time-dependent electronic state of the system is compared to the electronic ground state at the respective frozen-in ionic positions. This yields detailed information on the electronic excitations along the trajectory. This method has been applied to chemisorption of H-atoms on Al(111), with results consistent with the time-dependent Newns-Anderson model by Mizielinski and Bird [2]. In case of H/Si(001) we find an energy transfer into electron-hole pairs after one round-trip of the atom in front of the surface comparable to H/Al(111). We explain this unexpected result on the basis of the electronic structure. In case of HCl/Al(111) we find a significant coupling of the HCl molecular vibration to electron-hole pair excitations in the Al-substrate.

[1] A.M. Wodtke et al., Prog. Surf. Sci. 83, 167 (2008).

[2] D.M. Bird et al., Surf. Sci. 602, 1212 (2008).