Theoretical studies on clean and adsorbed surfaces of Ag-In-Yb

Abstract

The adsorption structure of Pb atoms on the five-fold surface of a AgInYb quasicrystal is studied using a first-principles calculation. The aperiodic five-fold surface is replaced by a cluster model, following the quasicrystal model by Takakura et al. The potential energy surface (PES) for a single Pb adsorption reflects the five-fold symmetry of the substrate. The most preferred adsorbed site is a five-fold hollow site surrounded by three In and two Yb atoms, and the most preferred sites form a pentagon with edge length 9.9 Å. The PES for the second adsorbed atom is calculated to examine the effects of interadsorbate interaction. It turns out that the interadsorbate interaction is limited, and it does not change the PES essentially. Thus, at low coverage, the Pb atoms presumably adsorb onto the five-fold hollow sites, forming a Pb pentagon with edge length 9.9 Å around the cluster center. Possible adsorption structures at higher coverage are also discussed.

Keywords:

• quasicrystals
• five-fold surface
• first-principles calculation
• Ag-In-Yb
• Pb
• adsorption
• potential energy surface

Acknowledgements

The authors appreciate discussions with M. Shimoda, H.R. Sharma, H. Takakura, C.P. Gómez and A.P. Tsai. Figures of the crystal structures are drawn by VESTA developed by K. Momma and F. Izumi 23. Calculations were partly carried out on SR11000 at the Supercomputer Center, Institute of Solid State Physics, University of Tokyo, and SX8 at YITP, Kyoto University.