Alkaline-earth metal monolayers on 5-fold i-Al-Pd-Mn surface: Influence of adatom size on quasiperiodic ordering

The structure and stability of a quasiperiodic alkaline-earth metal monolayer formed on a five-fold surface of an icosahedral Al–Pd–Mn quasicrystal have been investigated using ab initio density-functional methods. We study the influence of the size of the adatom on the regularity of the quasiperiodic ordering. It was found that Ca adatoms at a coverage 0.066 atoms/Ų (Θ = 0.5) form a highly regular quasiperiodic monolayer on the i-Al–Pd–Mn surface, with an ordering described by a decagonal DHBS tiling of decagons, hexagons, boats and pentagonal stars.