Bulk and surface structure of the clean and adsorbate-covered decagonal Al-Co-Ni quasicrystal

TL;DR

This paper combines experimental and computational studies to analyze the bulk and surface structures of decagonal Al-Co-Ni quasicrystals, demonstrating good agreement between models and experiments and exploring surface morphology variations.

Contribution

It introduces a structural model based on Al-Co clusters for decagonal Al-Co-Ni and validates it through experiments and molecular dynamics simulations.

Findings

Model aligns well with experimental bulk and surface properties.

Surface morphology varies with thermal relaxation rates.

Oxygen dissociative adsorption observed on the surface.

Abstract

We review our Al adsorption experiments on the tenfold-symmetry surface of the decagonal Al-Co-Ni quasicrystal and present computational simulations of adsorption on a structural model based on a fundamental Al-Co cluster with 20 \AA diameter, symmetry $\bar{10}2m$, and 8 \AA periodicity. This cluster is the building unit of $\tau ^2$-Al$_{13}$Co$_4$, from which, by a sequence of minor changes, the structures of the phases in the stability region of decagonal Al-Co-Ni can be derived. The model used for the decagonal Al$_{70}$Co$_{15}$Ni$_{15}$ is an idealized model with a two-layer periodicity (4 \AA) and no chemical or structural disorder. We find that the bulk and surface properties of this model are in good agreement with experiments. Our molecular-dynamics simulations of Al adsorption reproduce the experimental results and show that by varying the thermal relaxation rates of the adsorbed layer, a variety of different surface morphologies can be achieved. We also present our recent experiments on dissociative adsorption of oxygen on the decagonal surface.