The Equivalence Between Unit-Cell Twinning and Tiling in Icosahedral Quasicrystals

TL;DR

This paper demonstrates that tiling in icosahedral quasicrystals can be equivalently described by cyclic twinning at the unit cell level, linking structural tiling with twinning operations and Fibonacci-related periodicities.

Contribution

It establishes a direct equivalence between unit-cell twinning and tiling in icosahedral quasicrystals, providing a unified structural description.

Findings

Twinning operations on golden rhombohedra explain quasicrystal tiling.

Simulated diffraction matches experimental patterns.

Fibonacci series relates periodicities in the structure.

Abstract

It is shown that tiling in icosahedral quasicrystals can also be properly described by cyclic twinning at the unit cell level. The twinning operation is applied on the primitive prolate golden rhombohedra, which can be considered a result of a distorted face-centered cubic parent structure. The shape of the rhombohedra is determined by an exact space filling, resembling the forbidden five-fold rotational symmetry. Stacking of clusters, formed around multiply twinned rhombic hexecontahedra, keeps the rhombohedra of adjacent clusters in discrete relationships. Thus periodicities, interrelated as members of a Fibonacci series, are formed. The intergrown twins form no obvious twin boundaries and fill the space in combination with the oblate golden rhombohedra, formed between clusters in contact. Simulated diffraction patterns of the multiply twinned rhombohedra and the Fourier transform of an extended model structure are in full accord with the experimental diffraction patterns and can be indexed by means of three-dimensional crystallography.