This article reviews some of Ted Janssen's (1936-2017) major contributions to the field of aperiodic crystals. Aperiodic crystals are long-range ordered structures without 3D lattice translations and encompass incommensurately modulated phases, incommensurate composites and quasicrystals. Together with Pim de Wolff and Aloysio Janner, Ted Janssen invented the very elegant theory of superspace crystallography that, by adding a supplementary dimension to the usual 3D space, allows for a deeper understanding of the atomic structure of aperiodic crystals. He also made important contributions to the understanding of the stability and dynamics of aperiodic crystals, exploring their fascinating physical properties. He constantly interacted and collaborated with experimentalists, always ready to share and explain his detailed understanding of aperiodic crystals.
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http://dx.doi.org/10.1107/S2053273318016765 | DOI Listing |
Nat Commun
January 2025
Empa, Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland.
Studying the self-assembly of chiral molecules in two dimensions offers insights into the fundamentals of crystallization. Using scanning tunneling microscopy, we examine an uncommon aggregation of polyaromatic chiral molecules on a silver surface. Dense packing is achieved through a chiral triangular tiling of triads, with N and N ± 1 molecules at the edges.
View Article and Find Full Text PDFSci Rep
November 2024
Department of Physics, The University of Vermont, Burlington, VT, 05405, USA.
We investigate the band structure of metal-dielectric photonic crystals comprising stacked organic semiconductor microcavities with silver metal mirrors incorporating crystal defects: individual unit cells with aperiodic dimensionality. Both transfer matrix simulation and experimental verification are performed to investigate the impact on the photonic band structure as a single cavity is varied in size. The resulting mid-gap defect states are shown to hybridize with a photonic band at certain resonant dimensions.
View Article and Find Full Text PDFIUCrJ
November 2024
Structure Analysis, Institute of Physics of the Czech Academy of Sciences, Na Slovance 1999/2, Prague, 182 00, Czechia.
We draw attention to the exceptional work of Geers et al. [(2024). IUCrJ, 11, 910-920] on the analysis of magnetic phases, in which challenging magnetic structures are determined by a combination of modern computational methods and a connection between nuclear modulation and the ordering of magnetic moments is shown.
View Article and Find Full Text PDFNature
October 2024
Department of Physics, College of Science, Yonsei University, Seoul, Korea.
J Am Chem Soc
October 2024
Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, Oxford OX1 3QR, U.K.
We use synchrotron X-ray diffraction measurements to monitor the solvothermal crystallization mechanism of the aperiodic metal-organic framework TRUMOF-1. Following an initial incubation period, TRUMOF-1 forms as a metastable intermediate that subsequently transforms into an ordered product with triclinic crystal symmetry. We determine the structure of this ordered phase, which we call msw-TRUMOF-1, and show that it is related to TRUMOF-1 through topotactic reorganization of linker occupancies.
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