Five-dimensional structure refinement of decagonal Al65Cu20Co15

Abstract

A single-crystal X-ray structure analysis of decagonal Al₆₅ Cu₂₀Co₁₅ has been performed using the n-dimensional approach. The structure has been solved by Patterson analysis and subsequent least-squares refinement, both in the five-dimensional description. A final value of wR=0.097 for 259 independent reflections was achieved with I≥2σ(1) and 12 variables. There are three atoms in the asymmetric unit. The calculated density of the refined, structure model is ρ_c = 4.8 M gm ⁻³. The three-dimensional decagonal structure consists of two planar quasiperiodic layers, related by the tenfold screw axis, stacked periodically one upon the other. Characteristic large elements of the crystalline Al₁₃ Fe₄ structure type can be found in new combinations in the quasiperiodic layers. It is remarkable that pentagonal channels appear which are empty or occupied statistically.