Berlin 2012 – scientific programme

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O: Fachverband Oberflächenphysik

O 35: Poster Session II (Polymeric biomolecular films; Nanostructures; Electronic structure; Spin-orbit interaction; Phase transitions; Surface chemical reactions; Heterogeneous catalysis; Particles and clusters; Surface magnetism; Electron and spin dynamics; Surface dynamics; Methods; Electronic structure theory; Functional molecules)

O 35.89: Poster

Tuesday, March 27, 2012, 18:15–21:45, Poster B

Electronic energy dissipation - obtain mechanisms and models from TDDFT — •Michael Grotemeyer and Eckhard Pehlke — Institut für Theoretische Physik und Astrophysik, Universität Kiel, Germany

Molecular dynamics simulations based on time-dependent density-functional theory to describe the electron dynamics and Ehrenfest dynamics for the motion of the nuclei have provided detailed information about the electronic energy dissipation of vibrationally highly excited HCl molecules in front of a metal surface. Inspection of the time development of the electronic excitation spectra reveals the energy transfer mechanism and helps to identify the diabatic states responsible for the dissipation. The striking asymmetry between the excitation spectra of the holes and the electrons pinpoints the importance of the energetical position of the molecular resonances in the energy range of the unoccupied states. This leaves us with the question how to produce simple tight-binding like models and whether there is a unifying description of the energy dissipation process that holds the potential to be generalized to arbitrary molecular trajectories. Already a one-dimensional tight-binding model including only the LUMO is capable of describing the energy transfer process and illustrates many effects of the ab initio TDDFT-MD simulations. By adding an additional unoccupied molecular orbital into the model we obtain an improved description of the excitation spectra at the maximum of the dissipation. We suggest the resonance width of the LUMO plays a decisive role for the nonaddiabatic effects.