issue contents


ISSN: 2053-2733

Aperiodic 2018 special issue (March 2019)

Guest editors: Gloria Borgstahl, Alan I. Goldman and Patricia A. Thiel

This virtual special issue of Acta Crystallographica Section A features some highlights of the 9th Conference on Aperiodic Crystals (Aperiodic 2018) held at Iowa State University in July 2018, and brings together articles originally published in the January and March 2019 issues of the journal. The Aperiodic meetings are held every three years and are the flagship meetings of the Commission on Aperiodic Crystals (CAC) of the International Union of Crystallography (IUCr).

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Cover illustration: The channel of electron density along the c axis in the high-temperature disordered form of Fe2Al5, as modelled by Vinokur et al. [Acta Cryst. (2019), A75, 297–306].

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A collection of articles from presentations at the Aperiodic 2018 conference is introduced.

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This work examines the long-wavelength scaling properties of self-similar substitution tilings, placing them in their hyperuniformity classes. Quasiperiodic, non-PV (Pisot–Vijayaraghavan number) and limit-periodic examples are analyzed. Novel behavior is demonstrated for certain limit-periodic cases.

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Quantitative parameters of modulated crystal structures are determined from density functional theory calculations applied to superstructures obtained using the superspace formalism. The example of mullite is used to demonstrate that with this approach versatile aspects ranging from ordering phenomena to phase diagrams can be understood on a new level.

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Local potential differences between the 36 and vertex configurations are identified within a two-dimensional dodecagonal fullerene monolayer. In a local area of the 8/3 approximant, rotational switching fullerenes on 36 vertex sites are revealed by scanning tunneling microscopy.

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Ted Janssen's contributions to the field of aperiodic crystals are reviewed.

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The nucleation and growth dynamics of a decagonal quasicrystal and its approximant `X' phase are considered. Various similarities and differences are elucidated.

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The Fe2Al5 structure is remarkable among intermetallic phases for its channels of weakly ordered Al atoms. This article traces the origins of these channels to the cooperative effects of soft atomic motions dictated by chemical pressure quadrupoles and preferred electron concentrations.

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Analysis of a dodecagonal quasicrystal based on 8100 vertices from atomically resolved scanning tunnelling microscopy has been carried out. A detailed frequency and orientational analysis is presented for the triangle–square–rhomb tiling of a BaTiO3-derived quasicrystal.

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The physical significance of clusters in Al13TM4 compounds is invesitgated through ab initio methods based on density functional theory.
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