Testing bulk models of icosahedral quasicrystals with STM images of clean surfaces

Abstract

In the case of icosahedral Al-Pd-Mn we compare the STM (scanning tunnelling microscopy) image of the real fivefold surface to the STM simulations on the candidates of the fivefold bulk terminations. We make the choice of which termination fits best to the real image. It leads us to some hints important either for the chemistry of the bulk-model or for the eventual correction of the model of atomic positions itself. We work in the frame of the particular model of atomic positions, based on the diffraction data for Al₇₀Pd₂₁Mn₉ and Al₆₂Cu_25.5Fe_12.5. We also discuss the possibilities beyond this model.

Keywords:

• structure of quasicrystals
• clean surfaces
• STM

Acknowledgements

Z. Papadopolos thanks G. Kasner for the graphs presented in Figure 4, J. Ledieu for the STM image presented in Figure 3, and H. Reinhardt (University of Tübingen) for financial support. O. Gröning and R. Widmer thank M. Feuerbacher for providing the icosahedral Al-Pd-Mn monograin used in the STM work presented in Figure 6 and acknowledge financial support from the Swiss National Science Foundation (SNF) under contract 200021-112333/1.

Notes

Notes

1.  A model is deterministic if all the possible atomic positions are occupied by atoms.

2.  Under a thin layer we consider a layer of two or three planes of stacked atoms, on a distance significantly smaller than 0.86 Å. We treat such a layer as a single plane.