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Alfredo Metere, Peter Oleynikov, Mikhail Dzugutov, Sven Lidin
We report a solid smectic phase that exhibits dodecagonal global order. It is composed of axially stacked hexagonally ordered particle layers, and its 12-fold rotational symmetry induced by the 30° rotation of adjacent layers with respect to each other. A quasicrystal was produced in a molecular-dynamics simulation of a single-component system of particles interacting via a spherically-symmetric potential. It was formed as a result of a first-order phase transition from an isotropic liquid state that occurred under constant-density cooling...
September 16, 2016: Soft Matter
V Brajuskovic, F Barrows, C Phatak, A K Petford-Long
Artificial spin ice lattices have emerged as model systems for studying magnetic frustration in recent years. Most work to date has looked at periodic artificial spin ice lattices. In this paper, we observe frustration effects in quasicrystal artificial spin ice lattices that lack translational symmetry and contain vertices with different numbers of interacting elements. We find that as the lattice state changes following demagnetizing and annealing, specific vertex motifs retain low-energy configurations, which excites other motifs into higher energy configurations...
October 3, 2016: Scientific Reports
Joyce Pham, Andreas Kreyssig, Alan I Goldman, Gordon J Miller
A new icosahedral quasicrystalline phase, CaAu4.5-xAl1.5+x [0.11 ≤ x ≤ 0.40(6); CaAu4.4Al1.6, aQC = 5.383(4) Å, and Pm3̅ 5̅], and its lowest-order 1/0 cubic crystalline approximant phase, CaAu3+xAl1-x [0 ≤ x ≤ 0.31(1); a = 9.0766(5)-9.1261(8) Å, Pa3̅ (No. 205), and Pearson symbol cP40], have been discovered in the Ca-poor region of the Ca-Au-Al system. In the crystalline approximant, eight [Au3-xAl1+x] tetrahedra fill the unit cell, and each tetrahedron is surrounded by four Ca atoms, thus forming a three-dimensional network of {Ca4/4[Au3-xAl1+x]} tetrahedral stars...
October 17, 2016: Inorganic Chemistry
Xingchen Ye, Jun Chen, M Eric Irrgang, Michael Engel, Angang Dong, Sharon C Glotzer, Christopher B Murray
Expanding the library of self-assembled superstructures provides insight into the behaviour of atomic crystals and supports the development of materials with mesoscale order. Here we build on recent findings of soft matter quasicrystals and report a quasicrystalline binary nanocrystal superlattice that exhibits correlations in the form of partial matching rules reducing tiling disorder. We determine a three-dimensional structure model through electron tomography and direct imaging of surface topography. The 12-fold rotational symmetry of the quasicrystal is broken in sublayers, forming a random tiling of rectangles, large triangles and small triangles with 6-fold symmetry...
September 26, 2016: Nature Materials
S Förster, M Trautmann, S Roy, W A Adeagbo, E M Zollner, R Hammer, F O Schumann, K Meinel, S K Nayak, K Mohseni, W Hergert, H L Meyerheim, W Widdra
We report on the first observation of an approximant structure to the recently discovered two-dimensional oxide quasicrystal. Using scanning tunneling microscopy, low-energy electron diffraction, and surface x-ray diffraction in combination with ab initio calculations, the atomic structure and the bonding scheme are determined. The oxide approximant follows a 3^{2}.4.3.4 Archimedean tiling. Ti atoms reside at the corners of each tiling element and are threefold coordinated to oxygen atoms. Ba atoms separate the TiO_{3} clusters, leading to a fundamental edge length of the tiling 6...
August 26, 2016: Physical Review Letters
P Subramanian, A J Archer, E Knobloch, A M Rucklidge
We investigate the formation and stability of icosahedral quasicrystalline structures using a dynamic phase field crystal model. Nonlinear interactions between density waves at two length scales stabilize three-dimensional quasicrystals. We determine the phase diagram and parameter values required for the quasicrystal to be the global minimum free energy state. We demonstrate that traits that promote the formation of two-dimensional quasicrystals are extant in three dimensions, and highlight the characteristics required for three-dimensional soft matter quasicrystal formation...
August 12, 2016: Physical Review Letters
Heiko G Schoberth, Heike Emmerich, Markus Holzinger, Martin Dulle, Stephan Förster, Thomas Gruhn
Colloidal quasicrystals have received increased interest recently due to new insight in exploring their potential for photonic materials as well as for optical devices [Vardeny et al., Nat. Photonics, 2013, 7, 177]. Colloidal quasicrystals in aqueous solutions have been found in systems of micelles with impenetrable cores [Fischer et al., Proc. Natl. Acad. Sci. U. S. A., 2011, 108, 1810]. A simple model potential for micelle-micelle interaction is the step potential, which is infinite for core overlaps and constant for shell overlaps...
September 28, 2016: Soft Matter
Yu Zou, Pawel Kuczera, Alla Sologubenko, Takashi Sumigawa, Takayuki Kitamura, Walter Steurer, Ralph Spolenak
The discovery of quasicrystals three decades ago unveiled a class of matter that exhibits long-range order but lacks translational periodicity. Owing to their unique structures, quasicrystals possess many unusual properties. However, a well-known bottleneck that impedes their widespread application is their intrinsic brittleness: plastic deformation has been found to only be possible at high temperatures or under hydrostatic pressures, and their deformation mechanism at low temperatures is still unclear. Here, we report that typically brittle quasicrystals can exhibit remarkable ductility of over 50% strains and high strengths of ∼4...
2016: Nature Communications
J W Cahn
The discretely diffracting aperiodic crystals termed quasicrystals, discovered at NBS in the early 1980s, have led to much interdisciplinary activity involving mainly materials science, physics, mathematics, and crystallography. It led to a new understanding of how atoms can arrange themselves, the role of periodicity in nature, and has created a new branch of crystallography.
2001: Journal of Research of the National Institute of Standards and Technology
Haiming Yuan, Xiangqian Jiang, Feng Huang, Xiudong Sun
We numerically study the multiple excitation of surface modes in 2D photonic quasicrystal/metal/substrate structure. An improved rigorous coupled wave analysis method that can handle the quasicrystalline structure is presented. The quasicrystalline lattice, which refers to Penrose tiling in this paper, is generated by the cut-and-project method. The normal incidence spectrum presents a broadband multiple responses property. We find that the phase matching condition determines the excitation frequency for a given incident angle, while the depth of the reflection valley depends on the incident polarization...
2016: Scientific Reports
K Kajiwara, Y Matsui, T P Yadav, N K Mukhopadhyay, O N Srivastava
The present report describes the catalytic activity of mechanically activated nano quasicrystalline Al65Cu20Fe15 and related nano crystalline Al50Cu28Fe22 for the synthesis of carbon nanotubes (CNTs). CNTs are synthesized by catalytic decomposition of ethanol through nano quasicrystalline Al65Cu20Fe15 and related crystalline Al50Cu28Fe22 alloys as a catalyst. The synthesized multi-walled CNTs exhibits tube diameter ranging from 5 to 25 nm. The synthesized CNTs are characterized by scanning and transmission electron microscopy...
March 2016: Journal of Nanoscience and Nanotechnology
Tsunetomo Yamada, Hiroyuki Takakura, Holger Euchner, Cesar Pay Gómez, Alexei Bosak, Pierre Fertey, Marc de Boissieu
The detailed atomic structure of the binary icosahedral (i) ScZn7.33 quasicrystal has been investigated by means of high-resolution synchrotron single-crystal X-ray diffraction and absolute scale measurements of diffuse scattering. The average atomic structure has been solved using the measured Bragg intensity data based on a six-dimensional model that is isostructural to the i-YbCd5.7 one. The structure is described with a quasiperiodic packing of large Tsai-type rhombic triacontahedron clusters and double Friauf polyhedra (DFP), both resulting from a close-packing of a large (Sc) and a small (Zn) atom...
July 1, 2016: IUCrJ
Tsutomu Ishimasa
Higher-dimensional structure analysis of quasicrystals is now possible. Yamada et al. [IUCrJ (2016), 3, 247-258] have solved the atomic structure of icosahedral ScZn7.33 including the characteristic imperfections.
July 1, 2016: IUCrJ
D Luo, Y Li, X W Xu, Q G Du
We demonstrate mirrorless lasers based on all organic nanostructure fabricated by seven- and nine-beam interference using low contrast material, holographic polymer dispersed liquid crystals (H-PDLC). A finite-difference time-domain (FDTD) simulation is used to study the transmission of quasicrystal. The wavelengths of lasing peak are determined by both of local structure of quasicrystal that the pumping light experienced as well as the photoluminescence of laser dye doped. Features of mirrorless laser from quasicrystal based on H-PDLC include directional light source, low threshold, simple fabrication process, low cost and tunability...
May 30, 2016: Optics Express
I C Fulga, D I Pikulin, T A Loring
Weak topological phases are usually described in terms of protection by the lattice translation symmetry. Their characterization explicitly relies on periodicity since weak invariants are expressed in terms of the momentum-space torus. We prove the compatibility of weak topological superconductors with aperiodic systems, such as quasicrystals. We go beyond usual descriptions of weak topological phases and introduce a novel, real-space formulation of the weak invariant, based on the Clifford pseudospectrum. A nontrivial value of this index implies a nontrivial bulk phase, which is robust against disorder and hosts localized zero-energy modes at the edge...
June 24, 2016: Physical Review Letters
A T Cadotte, J Dshemuchadse, P F Damasceno, R S Newman, S C Glotzer
We report the formation of a binary crystal of hard polyhedra due solely to entropic forces. Although the alternating arrangement of octahedra and tetrahedra is a known space-tessellation, it had not previously been observed in self-assembly simulations. Both known one-component phases - the dodecagonal quasicrystal of tetrahedra and the densest-packing of octahedra in the Minkowski lattice - are found to coexist with the binary phase. Apart from an alternative, monoclinic packing of octahedra, no additional crystalline phases were observed...
September 14, 2016: Soft Matter
José I Urgel, David Écija, Guoqing Lyu, Ran Zhang, Carlos-Andres Palma, Willi Auwärter, Nian Lin, Johannes V Barth
The recognition of quasicrystals, which exhibit long-range order but lack translational symmetry, represented both the introduction of a new class of materials and a transformative breakthrough in crystallography. Concomitant with the exploration of quasicrystallinity, metal-organic architectures emerged as promising and versatile systems with significant application potential. Their building principles have been studied extensively and become manifest in a multitude of intricate amorphous and crystalline phases...
July 2016: Nature Chemistry
Paul D Asimow, Chaney Lin, Luca Bindi, Chi Ma, Oliver Tschauner, Lincoln S Hollister, Paul J Steinhardt
We designed a plate impact shock recovery experiment to simulate the starting materials and shock conditions associated with the only known natural quasicrystals, in the Khatyrka meteorite. At the boundaries among CuAl5, (Mg0.75Fe(2+) 0.25)2SiO4 olivine, and the stainless steel chamber walls, the recovered specimen contains numerous micron-scale grains of a quasicrystalline phase displaying face-centered icosahedral symmetry and low phason strain. The compositional range of the icosahedral phase is Al68-73Fe11-16Cu10-12Cr1-4Ni1-2 and extends toward higher Al/(Cu+Fe) and Fe/Cu ratios than those reported for natural icosahedrite or for any previously known synthetic quasicrystal in the Al-Cu-Fe system...
June 28, 2016: Proceedings of the National Academy of Sciences of the United States of America
Tianbao Yu, Zhong Wang, Wenxing Liu, Tongbiao Wang, Nianhua Liu, Qinghua Liao
We report numerically large and complete photonic and phononic band gaps that simultaneously exist in eight-fold phoxonic quasicrystals (PhXQCs). PhXQCs can possess simultaneous photonic and phononic band gaps over a wide range of geometric parameters. Abundant localized modes can be achieved in defect-free PhXQCs for all photonic and phononic polarizations. These defect-free localized modes exhibit multiform spatial distributions and can confine simultaneously electromagnetic and elastic waves in a large area, thereby providing rich selectivity and enlarging the interaction space of optical and elastic waves...
April 18, 2016: Optics Express
Siddharth Chanpuriya, Kyungtae Kim, Jingwen Zhang, Sangwoo Lee, Akash Arora, Kevin D Dorfman, Kris T Delaney, Glenn H Fredrickson, Frank S Bates
We report the phase behavior of a series of poly(styrene)-b-poly(isoprene)-b-poly(styrene)'-b-poly(ethylene oxide) (SIS'O) tetrablock terpolymers. This study was motivated by self-consistent field theory (SCFT) calculations that anticipate a rich array of sphere-forming morphologies with variations in the molecular symmetry parameter τ = NS/(NS + NS'), where N is the block degree of polymerization and the volume fraction of O is less than about 0.22. Eight SIS'O samples, with τ ranging from 0.21 to 0.73, were synthesized and investigated using small-angle X-ray scattering and transmission electron microscopy, yielding evidence of nine different spherical phases: hexagonal, FCC, HCP, BCC, rhombohedral (tentative), liquid-like packing, dodecagonal quasicrystal, and Frank-Kasper σ and A15 phases...
May 24, 2016: ACS Nano
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