Reconstruction of the Al 13 Ru 4 (010) Approximant Surface Leading to Anisotropic Molecular Adsorption

The atomic structure of the Al13Ru4(010) approximant surface, investigated for annealing temperatures ranging from 873 K to 1143 K, can be described by pentagonal motifs and vacancies. It exhibits an atypical surface reconstruction which manifests itself in real space by well-separated stripes running about 10○ off the [001] direction. Their mutual ordering is drastically improving at high annealing temperature. This is simultaneously accompanied by a filling of the pentagonal hollow sites present in the stripes with atoms or groups of atoms. We provide evidence that these unidirectional features are of true surface origin. The bulk electronic density of states calculated within the density functional theory framework matches the experimental valence band spectra. In addition to step edges, molecular adsorption reveals that stripes are initially the most reactive sites, leading to anisotropic island growth.