scholarly journals Unified structure theory of icosahedral quasicrystals: Evidence from neutron powder diffraction patterns that AlCrFeMnSi, AlCuLiMg, and TiNiFeSi icosahedral quasicrystals are twins of cubic crystals containing about 820 or 1012 atoms in a primitive unit cube

1988 ◽  
Vol 85 (22) ◽  
pp. 8376-8380 ◽  
Author(s):  
L. Pauling
Keyword(s):  
Powder Diffraction ◽  
Neutron Powder Diffraction ◽  
Unit Cube ◽  
Structure Theory ◽  
Cubic Crystals ◽  
Icosahedral Quasicrystals ◽  
Diffraction Patterns

Use of Neutron Diffraction for Describing Texture of Isostatically-Pressed Molybdite Powders

2005 ◽  
Vol 105 ◽  
pp. 83-88 ◽  
Author(s):  
H. Sitepu ◽  
Heinz Günter Brokmeier
Keyword(s):  
Crystal Structure ◽  
Neutron Diffraction ◽  
Powder Diffraction ◽  
Quantitative Description ◽  
Neutron Powder Diffraction ◽  
Powder Diffraction Data ◽  
Neutron Powder Diffraction Data ◽  
Pole Figures ◽  
Diffraction Patterns ◽  
Excellent Tool

The modelling and/or describing of texture (i.e. preferred crystallographic orientation (PO)) is of critical importance in powder diffraction analysis - for structural study and phase composition. In the present study, the GSAS Rietveld refinement with generalized spherical harmonic (GSH) was used for describing isostatically-pressed molybdite powders neutron powder diffraction data collected in the ILL D1A instrument. The results showed that for texture in a single ND data of molybdite the reasonable crystal structure parameters may be obtained when applying corrections to intensities using the GSH description. Furthermore, the WIMV method was used to extract the texture description directly from a simultaneous refinement with 1368 whole neutron diffraction patterns taken from the sample held in a variety of orientations in the ILL D1B texture goniometer. The results provided a quantitative description of the texture refined simultaneously with the crystal structure. Finally, the (002) molybdite pole-figures were measured using the GKSS TEX2 texture goniometer. The results showed that neutron diffraction is an excellent tool to investigate the texture in molybdite.

High-temperature structural evolution of hexagonal multiferroic YMnO3and YbMnO3

2007 ◽  
Vol 40 (4) ◽  
pp. 730-734 ◽  
Author(s):  
Il-Kyoung Jeong ◽  
N. Hur ◽  
Th. Proffen
Keyword(s):  
Phase Transition ◽  
High Temperature ◽  
Powder Diffraction ◽  
Structural Parameters ◽  
Structural Evolution ◽  
Neutron Powder Diffraction ◽  
Temperature Behaviour ◽  
Rietveld Refinements ◽  
Polar Structure ◽  
Diffraction Patterns

Neutron powder diffraction studies on the structural evolution of hexagonal multiferroic YMnO3and YbMnO3from 1000 K to 1400 K, and from 1000 K to 1350 K, respectively, are presented. The temperature evolution of diffraction patterns suggests that YMnO3undergoes a phase transition to a non-polar structure above 1200 K, while YbMnO3remains ferroelectric up to 1350 K. Detailed structural parameters were obtained as a function of temperature from Rietveld refinements. Based on this result, the distinct differences in temperature behaviour between YMnO3and YbMnO3, and the origin of the ferroelectricity in these hexagonal multiferroics are discussed.

scholarly journals Identifying and Indexing Icosahedral Quasicrystals from Powder Diffraction Patterns

2001 ◽  
Vol 87 (27) ◽  
Author(s):  
Peter J. Lu ◽  
Kenneth Deffeyes ◽  
Paul J. Steinhardt ◽  
Nan Yao
Keyword(s):  
Powder Diffraction ◽  
Icosahedral Quasicrystals ◽  
Diffraction Patterns

Refinement of the Crystal Structures of Palladium-rich In-Pd Compounds by X-Ray and Neutron Powder Diffraction

2007 ◽  
Vol 62 (7) ◽  
pp. 929-934 ◽  
Author(s):  
Holger Kohlmanna ◽  
Clemens Ritter
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Structure Type ◽  
Neutron Powder Diffraction ◽  
Type Model ◽  
Rietveld Refinements ◽  
X Ray ◽  
Neutron Powder Diffraction Data ◽  
Diffraction Patterns ◽  
Catalyzed Reactions

Abstract The ternary indium palladium intermetallics In3Pd5, InPd2, and InPd3 have been synthesized by iodine-catalyzed reactions from the elements. Rietveld refinements on X-ray powder diffraction patterns provide the first accurate crystal structure data for In3Pd5 (Pbam, No. 55, a = 1104.20(2), b = 561.346(8), c = 424.263(6) pm, Rh5Ge3-type) and InPd2 (Pnma, No. 62, a = 561.676(6), b = 421.710(4), c = 822.78(8) pm, Co2Si-type). X-Ray powder diffraction apparently confirms the TiAl3 structure type proposed in the literature for InPd3. However, Rietveld refinement on neutron powder diffraction data reveals an In/Pd distributional disorder. Therefore, we describe the crystal structure of InPd3 in a AuCu-type model instead (P4/mmm, No. 123, a = 287.224(4), c = 380.079(7) pm), with mixed occupancy of one crystallographic site by 50% In and 50% Pd. In contrast to In3Pd5 and InPd2, which can be considered to be line compounds, InPd3 shows a non-negligible homogeneity range with unit cell volumes ranging from 0.126132(5) nm3 for the indium-rich to 0.125474(8) nm3 for the palladium-rich In1+xPd3−x phases. Mean In-Pd distances in these indium palladium intermetallics range from 272.3 pm (In1 in In3Pd5) with coordination number 8 for indium to 281.2 pm for 12-coordinated In in InPd3.

High Resolution Neutron Powder Diffraction Study of the Tubular Phase Bi4Sr8Cu5O19+x

1989 ◽  
Vol 169 ◽  
Author(s):  
M.T. Caldés ◽  
J.M. Navarro ◽  
A. Fuertes ◽  
X. Obradors ◽  
C. Miravitlles ◽  
...  
Keyword(s):  
Structural Change ◽  
High Resolution ◽  
Neutron Diffraction ◽  
Diffraction Study ◽  
Powder Diffraction ◽  
Neutron Powder Diffraction ◽  
Diffraction Experiment ◽  
Antiferromagnetic Ordering ◽  
Powder Neutron Diffraction ◽  
Diffraction Patterns

AbstractA high resolution neutron powder diffraction experiment has been performed on Bi4Sr8Cu5O19+x. The structure is well described in the space group Fmmm with the oxygen atoms in the bismuth planes appearing disordered in intermediate positions between NaCl and bridging sites as occurs in the superconductors Bi2Sr2Can‐1CunO4n+2. Temperature dependence study of powder neutron diffraction patterns between 1.5K and 998K does not show any relevant structural change neither evidence of antiferromagnetic ordering in this sample.

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