Co-rich decagonal Al-Co-Ni: predicting structure, orientational order, and puckering

TL;DR

This paper predicts the atomic structure and orientational order of a Co-rich decagonal Al-Co-Ni quasicrystal using computational modeling, revealing insights into layer puckering and structural motifs.

Contribution

It introduces a systematic modeling approach combining Penrose tiling decoration and Monte Carlo annealing to predict quasicrystal structure and orientational order.

Findings

Network of edge-sharing decagons identified

Instability of four-layer structure towards puckering analyzed

Explains pentagonal orientational order in the structure

Abstract

We apply systematic methods previously used by Mihalkovic et al. to predict the structure of the `basic' Co-rich modification of the decagonal Al70 Co20 Ni10 layered quasicrystal, based on known lattice constants and previously calculated pair potentials. The modelling is based on Penrose tile decoration and uses Monte Carlo annealing to discover the dominant motifs, which are converted into rules for another level of description. The result is a network of edge-sharing large decagons on a binary tiling of edge 10.5 A. A detailed analysis is given of the instability of a four-layer structure towards $c$-doubling and puckering of the atoms out of the layers, which is applied to explain the (pentagonal) orientational order.