Temat: 61.44.Br - Prolib Integro

Skocz do pozycji: 1.

Tytuł:: An Icosahedral Quasicrystal as a Packing of Regular Tetrahedra
Autorzy:: Fang, F.
Kovacs, J.
Sadler, G.
Irwin, K.
Tematy:: 61.44.Br
61.46.-w; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1202974.pdf Link otwiera się w nowym oknie
Opis:: We present the construction of a dense, quasicrystalline packing of regular tetrahedra with icosahedral symmetry. This quasicrystalline packing was achieved through two independent approaches. The first approach originates in the Elser-Sloane 4D quasicrystal. A 3D slice of the quasicrystal contains a few types of prototiles. An initial structure is obtained by decorating these prototiles with tetrahedra. This initial structure is then modified using the Elser-Sloane quasicrystal itself as a guide. The second approach proceeds by decorating the prolate and oblate rhombohedra in a 3-dimensional Ammann tiling. The resulting quasicrystal has a packing density of 59.783%. We also show a variant of the quasicrystal that has just 10 "plane classes" (compared with the 190 of the original), defined as the total number of distinct orientations of the planes in which the faces of the tetrahedra are contained. This small number of plane classes was achieved by a certain "golden rotation" of the tetrahedra.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 2.

Tytuł:: Structure Model for Icosahedral Quasicrystal Based on Ammann Tiling
Autorzy:: Strzałka, R.
Wolny, J.
Tematy:: 61.44.Br
61.50.Ah; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1203441.pdf Link otwiera się w nowym oknie
Opis:: We derive a structure model for icosahedral quasicrystals. The model is based on a statistical approach involving the concept of average unit cell. This approach enables limiting calculations to real space as opposed to higher-dimensional analysis involving to unphysical atomic surface modeling. We start with the three-dimensional Ammann tiling with its two rhombohedral prototiles. For monoatomic decoration of the lattice nodes the perfect agreement with the higher-dimensional description was recently shown. In this paper we discuss the shape of the average unit cell and the first attempts for decoration scheme.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 3.

Tytuł:: Simple decoration model of icosahedral quasicrystals in statistical approach
Autorzy:: Strzalka, R.
Buganski, I.
Wolny, J.
Tematy:: 61.44.Br
61.50.Ah; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1112766.pdf Link otwiera się w nowym oknie
Opis:: The statistical approach based on the average unit cell concept was recently successfully applied to structural modelling of icosahedral quasicrystals. The structure factor for arbitrarily decorated icosahedral structure was derived for model Ammann tiling (3D Penrose tiling). It is a fully physical-space model where no higher-dimensional description is needed. In the present paper we show the application of the model to the so-called simple decoration scheme - atomic decoration in the nodes, at mid-edges and along body-diagonal of structural units of 3D Penrose tiling. By analyzing the obtained calculated diffraction patterns we show the correctness of the model and its applicability to binary and ternary icosahedral phases.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 4.

Tytuł:: Discrete Tomography: Magic Numbers for N-Fold Symmetry
Autorzy:: Huck, C.
Moll, M.
Nilsson, J.
Tematy:: 61.43.-j
61.44.Br; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1372751.pdf Link otwiera się w nowym oknie
Opis:: We consider the problem of distinguishing convex subsets of n-cyclotomic model sets Λ by (discrete parallel) X-rays in prescribed Λ-directions. In this context, a 'magic number' $m_{Λ}$ has the property that any two convex subsets of Λ can be distinguished by their X-rays in any set of $m_{Λ}$ prescribed Λ-directions. Recent calculations suggest that (with one exception in the case n=4) the least possible magic number for n-cyclotomic model sets might just be N+1, where N=lcm(n,2).
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 5.

Tytuł:: Tsai-Type Quasicrystal and Its Approximant in Au-Al-Tm Alloys
Autorzy:: Tanaka, K.
Tanaka, Y.
Ishimasa, T.
Nakayama, M.
Matsukawa, S.
Deguchi, K.
Sato, N.
Tematy:: 61.66.Dk
61.44.Br; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1373678.pdf Link otwiera się w nowym oknie
Opis:: A P-type icosahedral quasicrystal with a six-dimensional lattice parameter $a_{6D}$ = 7.411 Å is formed as an equilibrium phase in Au-Al-Tm alloy, of which composition was analyzed to be $Au_{46}Al_{38}Tm_{16}$ by electron probe microanalysis. This quasicrystal is observed as a predominant phase in both as-cast and $Au_{49}Al_{34}Tm_{17}$ alloys annealed at 910°C, and as one of main phases in the alloy slowly cooled from 1020°C. A 1/1 approximant, $Au_{48}Al_{38}Tm_{14}$, is also formed near the composition of the quasicrystal. This is a body-centered cubic structure (space group: Im3̅) with a lattice parameter a = 14.458 Å that is an isostructure to the recently reported 1/1 Tsai-type approximant in Au-Al-Yb. This approximant is characterized by disorderly arranged four Au-Al atoms centered at the Tsai-type cluster, presence of atoms at 8c site, and chemical ordering of Au and Al at sites forming a partial triacontahedron.
Dostawca treści:: Biblioteka Nauki

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na półce

Skocz do pozycji: 6.

Tytuł:: Fitting the long-range order of a decagonal quasicrystal
Autorzy:: Chodyń, M.
Kuczera, P.
Wolny, J.
Tematy:: 61.44.Br; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1075925.pdf Link otwiera się w nowym oknie
Opis:: The generalized Penrose tiling is an infinite set of decagonal tilings. It is constructed with the same rhombs (thick and thin) as the conventional Penrose tiling, but its long-range order depends on the so-called shift parameter sın łangle 0,1). The formula for structure factor, calculated within the average unit cell approach, works in physical space only and is directly dependent on the s parameter. It allows to straightforwardly change the long-range order of the refined structure just by changing the s parameter and keeping the tile decoration unchanged. The possibility and viability of using the shift as one of the refinement parameters during structure refinement was tested for a numerically generated simple binary decagonal quasicrystal.
Dostawca treści:: Biblioteka Nauki

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na półce

Skocz do pozycji: 7.

Tytuł:: Multidimensional "Paperfolding" Structures - Three and Four Dimensions
Autorzy:: Ben-Abraham, S.
Flom, D.
Richman, R.
Shapira, D.
Tematy:: 61.44.Br; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1202904.pdf Link otwiera się w nowym oknie
Opis:: We recapitulate our previously developed recursive algorithm for creating "paperfolding" structures in arbitrary dimensions. Here we explain and apply it specifically to three and four dimensions. We visualize the results by suitable projections. We also explicitly enumerate the number of "folds" in the first four generations of the recursion. We conjecture (without proof) that the Fourier spectrum of the structures is pure point (the Bragg peaks).
Dostawca treści:: Biblioteka Nauki

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na półce

Skocz do pozycji: 8.

Tytuł:: Direct and Reciprocal Space Properties of the Generalized Penrose Tiling
Autorzy:: Chodyń, M.
Kuczera, P.
Wolny, J.
Tematy:: 61.44.Br; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1202908.pdf Link otwiera się w nowym oknie
Opis:: We have constructed a generalized Penrose tiling by the cut-and-project method and compared its structure with that of the regular Penrose tiling. We derived the structure factor of the generalized Penrose tiling and applied it to calculate the diffraction pattern of a non-decorated structure.
Dostawca treści:: Biblioteka Nauki

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na półce

Skocz do pozycji: 9.

Tytuł:: Finite Element Method for Static Problems of Cubic Quasicrystals
Autorzy:: Yang, L.
He, F.
Gao, Y.
Tematy:: 61.44.Br; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1202985.pdf Link otwiera się w nowym oknie
Opis:: We put forward a finite element method for static problems of cubic quasicrystals by variation of a suitable general potential functional. As an example we study a quasicrystal column containing a penny-shaped crack. The comparison with analytical results shows that the precision and efficiency of the numerical solution are satisfactory. The procedure can be used to solve more complicated boundary value problems and can be extended towards more sophisticated methods of crack tip loading analysis.
Dostawca treści:: Biblioteka Nauki

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na półce

Skocz do pozycji: 10.

Tytuł:: Topological Bragg Peaks and How They Characterise Point Sets
Autorzy:: Kellendonk, J.
Tematy:: 61.44.Br; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1203066.pdf Link otwiera się w nowym oknie
Opis:: The positions of the Bragg peaks in point set diffraction show up as eigenvalues of a dynamical system. Topological Bragg peaks arise from topological eigenvalues and determine the torus parametrisation of the point set. We will discuss how qualitative properties of the torus parametrisation characterise the point set.
Dostawca treści:: Biblioteka Nauki

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