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K Kamiya, T Takeuchi, N Kabeya, N Wada, T Ishimasa, A Ochiai, K Deguchi, K Imura, N K Sato
Superconductivity is ubiquitous as evidenced by the observation in many crystals including carrier-doped oxides and diamond. Amorphous solids are no exception. However, it remains to be discovered in quasicrystals, in which atoms are ordered over long distances but not in a periodically repeating arrangement. Here we report electrical resistivity, magnetization, and specific-heat measurements of Al-Zn-Mg quasicrystal, presenting convincing evidence for the emergence of bulk superconductivity at a very low transition temperature of [Formula: see text] K...
January 11, 2018: Nature Communications
Joyce Pham, Fanqiang Meng, Matthew J Lynn, Tao Ma, Andreas Kreyssig, Matthew J Kramer, Alan I Goldman, Gordon J Miller
The irreversible transformation from an icosahedral quasicrystal (i-QC) CaAu4.39Al1.61 to its cubic 2/1 crystalline approximant (CA) Ca13Au56.31(3)Al21.69 (CaAu4.33(1)Al1.67, Pa ̅ 3(No. 205); Pearson symbol: cP728; a = 23.8934(4) Å), starting at ~570 ○C and complete by ~650 ○C, is discovered from in-situ, high-energy, variable-temperature powder X-ray diffraction (PXRD), thereby providing direct experimental evidence for the relationship between QCs and their associated CAs. The new cubic phase crystallizes in a Tsai-type approximant structure under the broader classification of polar intermetallic compounds, in which atoms of different electronegativities, viz...
December 29, 2017: Journal of the American Chemical Society
Qisheng Lin, Gordon J Miller
Intermetallic compounds represent an extensive pool of candidates for energy related applications stemming from magnetic, electric, optic, caloric, and catalytic properties. The discovery of novel intermetallic compounds can enhance understanding of the chemical principles that govern structural stability and chemical bonding as well as finding new applications. Valence electron-poor polar intermetallics with valence electron concentrations (VECs) between 2.0 and 3.0 e-/atom show a plethora of unprecedented and fascinating structural motifs and bonding features...
December 18, 2017: Accounts of Chemical Research
Insung Han, Xianghui Xiao, Ashwin J Shahani
How does a quasicrystal grow? Despite the decades of research that have been dedicated to this area of study, it remains one of the fundamental puzzles in the field of crystal growth. Although there has been no lack of theoretical studies on quasicrystal growth, there have been very few experimental investigations with which to test their various hypotheses. In particular, evidence of the in situ and three-dimensional (3D) growth of a quasicrystal from a parent liquid phase is lacking. To fill-in-the-gaps in our understanding of the solidification and melting pathways of quasicrystals, we performed synchrotron-based X-ray imaging experiments on a decagonal phase with composition of Al-15at%Ni-15at%Co...
December 12, 2017: Scientific Reports
Mengjie Zu, Peng Tan, Ning Xu
In traditional approaches to form quasicrystals, multiple competing length scales involved in particle size, shape, or interaction potential are believed to be necessary. It is unexpected that quasicrystals can be formed by monodisperse, isotropic particles interacting via a simple potential that does not contain explicit multiple length scales to stabilize quasicrystals. Here, we report the surprising finding of the formation of such quasicrystals in high-density systems of soft-core particles. Although there are length scales naturally introduced in our model systems, they do not establish the quasicrystalline order...
December 12, 2017: Nature Communications
A Dareau, E Levy, M Bosch Aguilera, R Bouganne, E Akkermans, F Gerbier, J Beugnon
Topological properties of crystals and quasicrystals is a subject of recent and growing interest. This Letter reports an experiment where, for certain quasicrystals, these properties can be directly retrieved from diffraction. We directly observe, using an interferometric approach, all of the topological invariants of finite-length Fibonacci chains in their diffraction pattern. We also quantitatively demonstrate the stability of these topological invariants with respect to structural disorder.
November 24, 2017: Physical Review Letters
Julius Oppenheim, Chi Ma, Jinping Hu, Luca Bindi, Paul J Steinhardt, Paul D Asimow
Five-component icosahedral quasicrystals with compositions in the range Al68-73Fe11-16Cu10-12Cr1-4Ni1-2 were recently recovered after shocking metallic CuAl5 and (Mg0.75Fe0.25)2SiO4 olivine in a stainless steel 304 chamber, intended to replicate a natural shock that affected the Khatyrka meteorite. The iron in those quasicrystals might have originated either from reduction of Fe(2+) in olivine or from the stainless steel chamber. In this study, we clarify the shock synthesis mechanism of icosahedral quasicrystals through two new shock recovery experiments...
November 15, 2017: Scientific Reports
J Oppenheim, C Ma, J Hu, L Bindi, P J Steinhardt, P D Asimow
The Khatyrka meteorite contains both icosahedral and decagonal quasicrystals. In our previous studies, icosahedral quasicrystals have been synthesized and recovered from shock experiments at the interface between CuAl5 and stainless steel 304 alloys. In this study, we report a new shock recovery experiment aimed at synthesizing decagonal quasicrystals similar to decagonite, natural Al71Ni24Fe5. Aluminum 2024 and permalloy 80 alloys were stacked together and shocked in a stainless steel 304 recovery chamber...
November 15, 2017: Scientific Reports
Abdullah Sirindil, Marianne Quiquandon, Denis Gratias
An analysis is presented of the new types of defects that can appear in crystalline structures where the positions of the atoms and the unit cell belong to the same {\bb Z}-module, i.e. are irrational projections of an N > 3-dimensional (N-D) lattice Λ as in the case of quasicrystals. Beyond coherent irrationally oriented twins already discussed in a previous paper [Quiquandon et al. (2016). Acta Cryst. A72, 55-61], new two-dimensional translational defects are expected, the translation vectors of which, being projections of nodes of Λ, have irrational coordinates with respect to the unit-cell reference frame...
November 1, 2017: Acta Crystallographica. Section A, Foundations and Advances
M Valliammai, S Sivabalan
We report a polarization maintaining chalcogenide (ChG) photonic quasicrystal fiber (PQF) for wide-band mid-IR (MIR) supercontinuum (SC) generation. The numerical demonstration of SC generation in the proposed PQF spans from 2 to 15 μm wavelengths for a pulse power of 2 kW. Besides, the proposed PQF offers a high birefringence (10(-3) to 10(-2)) from 3.5 to 15 μm wavelengths and exhibits a low confinement loss (10(-7) to 10(-1)) for the wavelengths from 2 to 15 μm with single mode behavior. The proposed Ge11...
June 1, 2017: Applied Optics
Zongdai Liu, Rui Chen, Yanjun Liu, Xinhai Zhang, Xiaowei Sun, Wenbin Huang, Dan Luo
Organic microcavity lasers based on liquid crystals have attracted substantial attention due to their easy processing, compact volume and excellent tunable properties. However, the threshold of traditional holographic polymer dispersed liquid crystals (H-PDLCs) laser doped with dye is usually as high as several tens of μJ/pulse, which hinders its broad applications. Herein, we demonstrate a low-threshold lasing from quasicrystal based on H-PDLCs. An conjugated polymer poly (2-methoxy-5-(2'-ethyl-hexyloxy)-p-phenylenevinylene (MEH-PPV) film is coated on the inner surface of glass substrate to dramatically reduce the lasing threshold, which is 20 times lower than that of dye-doped microcavity laser...
September 4, 2017: Optics Express
Quanlong Yang, Jianqiang Gu, Yuehong Xu, Yanfeng Li, Xueqian Zhang, Zhen Tian, Chunmei Ouyang, Jiaguang Han, Weili Zhang
The control of light-matter interaction in metasurfaces offers an unexplored potential for the excitation and manipulation of light. Here, we combine experimental terahertz time-domain spectroscopy and near-field scanning terahertz microscopy to demonstrate the role of reciprocal vectors in the transmission and plasmonic resonances of quasicrystal metasurfaces. An investigation of two-dimensional metasurface structures with different rotationally symmetric quasicrystal arrangements demonstrates that the transmission minima resulting from Wood's anomaly are directly related to the surface plasmon resonances...
October 2, 2017: Optics Express
Albert Prodan, Ram Dušić Hren, Marion A van Midden, Herman J P van Midden, Erik Zupanič
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...
September 29, 2017: Scientific Reports
V A Levashov
The behavior of identical particles interacting through the harmonic-repulsive pair potential has been studied in 3D using molecular dynamics simulations at a number of different densities. We found that at many densities, as the temperature of the systems decreases, the particles crystallize into complex structures whose formation has not been anticipated in previous studies on the harmonic-repulsive pair potential. In particular, at certain densities, crystallization into the structure Ia3¯d (space group #230) with 16 particles in the unit cell occupying Wyckoff special positions (16b) was observed...
September 21, 2017: Journal of Chemical Physics
Harini Pattabhiraman, Marjolein Dijkstra
We investigate the behaviour of a system of colloidal particles interacting with a hard-core and a repulsive square shoulder potential under the influence of a gravitational field using event-driven Brownian dynamics simulations. We use a fixed square shoulder diameter equal to 1.4 times the hard-core diameter of the colloids, for which we have previously calculated the equilibrium phase diagram considering two-dimensional disks [H. Pattabhiraman et al., J. Chem. Phys. 143, 164905 (2015) and H. Pattabhiraman and M...
September 14, 2017: Journal of Chemical Physics
Yao Sun, Kai Ma, Teresa Kao, Katherine A Spoth, Hiroaki Sai, Duhan Zhang, Lena F Kourkoutis, Veit Elser, Ulrich Wiesner
Considerable progress in the fabrication of quasicrystals demonstrates that they can be realized in a broad range of materials. However, the development of chemistries enabling direct experimental observation of early quasicrystal growth pathways remains challenging. Here, we report the synthesis of four surfactant-directed mesoporous silica nanoparticle structures, including dodecagonal quasicrystalline nanoparticles, as a function of micelle pore expander concentration or stirring rate. We demonstrate that the early formation stages of dodecagonal quasicrystalline mesoporous silica nanoparticles can be preserved, where precise control of mesoporous silica nanoparticle size down to <30 nm facilitates comparison between mesoporous silica nanoparticles and simulated single-particle growth trajectories beginning with a single tiling unit...
August 15, 2017: Nature Communications
Tomonari Dotera, Shinichi Bekku, Primož Ziherl
The most striking feature of conventional quasicrystals is their non-traditional symmetry characterized by icosahedral, dodecagonal, decagonal or octagonal axes. The symmetry and the aperiodicity of these materials stem from an irrational ratio of two or more length scales controlling their structure, the best-known examples being the Penrose and the Ammann-Beenker tiling as two-dimensional models related to the golden and the silver mean, respectively. Surprisingly, no other metallic-mean tilings have been discovered so far...
October 2017: Nature Materials
Ruibin Zhang, Xiangbing Zeng, Goran Ungar
We performed an atomic force microscopy study of the dendron-based dodecagonal quasicrystal, the material that had been reported in 2004 as the first soft quasicrystal. We succeeded in orienting the 12-fold axis perpendicular to the substrate, which allowed the imaging of the quasiperiodic xy plane. Thus for the first time we have been able to obtain direct real-space information not only on the arrangement of the tiles, but also on their 'decorations' by the individual spherical micelles or 'nanoatoms'. The high-resolution patterns recorded confirm the square-triangle tiling, but the abundance of different nodes corresponds closely to random tiling rather than to any inflation rule...
July 24, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Roman Ryltsev, Nikolay Chtchelkatchev
Using molecular dynamics simulations, we study computational self-assembly of one-component three-dimensional dodecagonal (12-fold) quasicrystals in systems with two-length-scale potentials. Existing criteria for three-dimensional quasicrystal formation are quite complicated and rather inconvenient for particle simulations. So to localize numerically the quasicrystal phase, one should usually simulate over a wide range of system parameters. We show how to universally localize the parameter values at which dodecagonal quasicrystal order may appear for a given particle system...
July 26, 2017: Soft Matter
Laura C Collins, Thomas G Witte, Rochelle Silverman, David B Green, Kenjiro K Gomes
Quasicrystals possess long-range order but lack the translational symmetry of crystalline solids. In solid state physics, periodicity is one of the fundamental properties that prescribes the electronic band structure in crystals. In the absence of periodicity and the presence of quasicrystalline order, the ways that electronic states change remain a mystery. Scanning tunnelling microscopy and atomic manipulation can be used to assemble a two-dimensional quasicrystalline structure mapped upon the Penrose tiling...
June 22, 2017: Nature Communications
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