The adsorption of Xe and Ar on quasicrystalline Al-Ni-Co

An interaction potential energy between an adsorbate (Xe and Ar) and the ten-fold Al-Ni-Co quasicrystal is computed by summing over all adsorbate-substrate interatomic interactions. The quasicrystal atoms' coordinates are obtained from LEED experiments, and the Lennard-Jones parameters of Xe-Al, Xe-Ni and Xe-Co are found using semiempirical combining rules. The resulting potential energy function of position is highly corrugated. Monolayer adsorption of Xe and Ar on the quasicrystal surface is investigated in two cases: (1) in the limit of low coverage (Henry's law regime), and (2) at somewhat larger coverage, when interactions between adatoms are considered through the second virial coefficient, C-AAS. A comparison with adsorption on a flat surface indicates that the corrugation enhances the effect of the Xe-Xe (Ar-Ar) interactions. The theoretical results for the low coverage adsorption regime are compared to experimental (LEED isobar) data.