Ordering and growth of Xe films on the 10-fold quasicrystalline approximant Al13Co4(100) surface

Abstract

Xe adsorption on the (100) surface of the complex alloy Al 13 Co 4 has been carried out using lowenergy electron diffraction (LEED) and grand canonical Monte Carlo (GCMC) simulations. This surface is an approximant to the 10-fold surface of decagonal Al-Ni-Co, on which Xe adsorption had been studied earlier. The adsorption behavior on the periodic surface is largely similar to that on the quasicrystal (layer-by-layer growth, hexagonal ordering near the onset of the 2 nd-layer adsorption) but also has some differences, such as the complete lack of registry of the Xe layer with the substrate structure in the hexagonal phase, and a high sensitivity of the Xe epitaxial direction to trace impurities. An ordering transition between the low-density and highdensity monolayer regimes was observed in the simulations, which involves a uniaxial compression of the monolayer film. Al 13 Co 4 has 102 atoms per unit cell, and its orthorhombic lattice parameters are a = 8.158 Å, b = 12.342 Å and c = 14.452 Å as determined from x-ray diffraction 23. Its structure along the [100] direction can be described as the stacking of two types of layers, flat (F) having 17 Al and 8 Co atoms, and puckered (P), having 22 Al and 4 Co atoms. There are two types of each plane,

Gas–Surface Interactions on Quasicrystals

“…In addition to simulation studies on realistic lubricants, it would be also useful to compare the ordering on periodic complex alloy surfaces, since quasicrystalline coatings are likely to contain such particles. To this end, we have begun to study the adsorption of rare gases on the Al 13 Co 4 (100) surface,37 which is an approximant of the tenfold Al‐Co‐Ni quasicrystal surface, and have found that a similar transition occurs for Xe on this surface 38. This suggests that the conclusions concerning the ordering of gases on quasicrystals can be applied to periodic complex metallic alloy surfaces.…”

Ordering and growth of rare gas films (Xe, Kr, Ar, and Ne) on the pseudo-ten-fold quasicrystalline approximant Al13Co4(100) surface

“…A detailed description of GCMC applied to rare gas adsorption can be obtained from previous publications [9][10][11]. Briefly, the equilibrium number of adsorbed atoms N , at a volume V and a temperature T , is determined using Metropolis Monte Carlo as a function of the chemical potential, µ, of the adsorbed film.…”

“…Quasicrystals, unlike periodic crystals, may possess five-fold or ten-fold symmetry axes that produce five-fold or ten-fold diffraction patterns due to their positional and orientational symmetries [2]. Due to their extraordinary material properties [3], they have attracted much attention from researchers in the field, including studies directed at understanding the growth and ordering of atoms adsorbed on the quasicrystalline surfaces [6][7][8][9][10][11][12][13]. Experimental observations and Monte Carlo simulations of charged colloidal particles in a two-dimensonal decagonal potential have produced much insight into the ordering, phase transitions, and other phenomena that occur for various interaction strengths, demonstrating a rich phase behavior that can provide insight into quasicrystal formation [4,5].…”

“…The periodicity of these materials greatly facilitates the determination of their surface structures, which can be determined precisely [17] without the need for extensive averaging or approximations [5,[18][19][20][21]. In an earlier electron diffraction study of the adsorption of Xe on the surface of the Al 13 Co 4 (100) quasicrystalline approximant [11], it was concluded that, similarly to Xe on the quasicrystal, the Xe initially takes the structure of the substrate, but achieves long-range order of nearly hexagonal symmetry at completion of the monolayer.…”

“…The adsorption of Kr, Ar, and Ne on the Al 13 Co 4 (100) surface is investigated using grand canonical Monte Carlo (GCMC) simulations [9][10][11]. The Al 13 Co 4 unit cell has lattice constants a = 8.158 Å, b = 12.342 Å, and c = 14.452 Å [22] and contains 102 atoms.…”