A DFT study of the adsorption of Au on Ni(111)

Recent experimental STM studies for the adsorption of Au/Ni(111) display a broken symmetry in the obtained STM pictures. Therefore, we have studied the adsorption phenomena of Au on Ni(111) using the Density Functional Theory, employing a plane wave basis set. To solve the Kohn-Sham equations, we have used the Vienna ab-initio simulation package (VASP). We have concentrated on the investigation of the structural and electronical properties of the system. The system has been modeled by four layers of Ni with nine atoms per layer forming a p(3x3) superstructure (resulting in a coverage of Au of about 0.11ML), separated by a vacuum layer more than 30 Å. In all cases, the two topmost Ni layers were allowed to relax. Brillouin zone integrations have been performed using a 5x5x1 Monkhorst-Pack grid. We have investigated an adsorption of Au in the high-symmetry sites; i.e. the top, bridge and fcc/hcp hollow positions. We found that the fcc hollow position is favored from an energetic point of view. Calculations for a higher coverage, resulting in a p(2x2) superstructure, lead to the same results. An analysis of the density of states (DOS) allows a characterization of the electronic properties of the adsorption. The adsorption is determined by an interaction of the Ni dyz, dxz and dz^2 with the Au d-orbitals. Furthermore, the experimental STM pictures will be confronted with pictures simulated from our calculations. Contact person: Konstantinos Termentzidis e-mail: [email protected] fax: 0043.1.42779514 Poster ECSCD-8 18-21 July, 2004 (Segovia, Spain) Pic 1. Simulated STM picture (constant current) for Au 0.11ML on Ni(111). The picture is simulated with a bias voltage of 0.4 eV for the hcp hollow position. 1. G.Kresse, J.Hafner, Phys. Rev. B 48 (1993), 13115 2. G.Kresse,J.Furtmueller, Computational Material Science6 (1996), 15 3. G.Kresse,J.Furtmueller, Phys. Rev. B 54 (1996), 11169 4. H.J. Monkhorst, J.D. Pack, Phys.Rev. B 13 (1972), 5188 Poster ECSCD-8 18-21 July, 2004 (Segovia, Spain)