scholarly journals Average structures of the disordered β-phase of Pigment Red 170: a single-crystal X-ray diffraction study

2014 ◽  
Vol 70 (2) ◽  
pp. 283-295 ◽  
Author(s):  
Rangana Warshamanage ◽  
Anthony Linden ◽  
Martin U. Schmidt ◽  
Hans-Beat Bürgi
Keyword(s):  
Single Crystal ◽  
Diffuse Scattering ◽  
Bragg Diffraction ◽  
X Ray Diffraction ◽  
Group Setting ◽  
X Ray ◽  
Space Groups ◽  
Average Structure ◽  
Β Phase ◽  
Layer Stacking

The β-phase of the industrially important Pigment Red 170 (β-P.R. 170) has a structure with severe layer stacking disorder. The single-crystal X-ray diffraction pattern consists of a difficult-to-disentangle mix of Bragg diffraction superimposed on rods of diffuse scattering which impede the estimation of accurate Bragg intensities. Two average monoclinic structure models with the same unit-cell dimensions, but different extents of disorder in the layers and different space groups seem plausible, one with the non-conventional space group settingB21/g(No. 14,Z′ = 2) and one inP21/a(No. 14,Z′ = 4). Disordered molecules related by a translation of 0.158bare present in all layers of theB21/gmodel and in every second layer of theP21/amodel. Layer-to-layer contacts are practically the same in both models. According to order–disorder theory, both models are valid superposition structures. Structure-factor calculations show that the pattern of strong and weak Bragg reflections is very similar for the two models.Rfactors indicate that theB21/gmodel is the most economic representation of the average structure. However, given the limitations in data processing, theP21/amodel should not be discarded and further insight sought from a detailed analysis of the experimental diffuse scattering. The difficulties encountered in this analysis raise the question of whether or not the concept of an average structure is applicable in practice to β-P.R. 170.

New layered supertetrahedral compounds T2-MSiAs2, T3-MGaSiAs3 and polytypic T4-M4Ga5SiAs9 (M = Sr, Eu)

2020 ◽  
Vol 75 (11) ◽  
pp. 983-989
Author(s):  
Valentin Weippert ◽  
Arthur Haffner ◽  
Dirk Johrendt
Keyword(s):  
Electrical Resistivity ◽  
Solid State ◽  
Single Crystal ◽  
Hall Effect ◽  
Optical Band Gap ◽  
Solid State Reactions ◽  
X Ray Diffraction ◽  
X Ray ◽  
Space Groups ◽  
Layer Stacking

AbstractThe new supertetrahedral compounds MSiAs2, MGaSiAs3 and mC/tI-M4Ga5SiAs9 (M = Sr, Eu) have been synthesized by solid-state reactions at high temperatures. The structures were determined by single crystal or powder X-ray diffraction. MSiAs2 and MGaSiAs3 crystallize in the monoclinic TlGaSe2- and RbCuSnS3-type structures, respectively (space group C2/c). These are topologically hierarchical variants of the tetragonal HgI2-type structure with stacked layers of T2 or T3 supertetrahedra. The T4 compounds M4Ga5SiAs9 are dimorphic and form new structure types in the space groups C2/c and I41/amd, respectively. The latter exhibits coinciding layer stacking as known from tetragonal HgI2. The T4 compounds close the gap between the longer known T2 types and the recently reported compounds with T5 and T6 supertetrahedra. Measurements of the optical band gap, electrical resistivity and Hall Effect support the semiconducting nature of M4Ga5SiAs9. Magnetization measurements confirm Eu2+ in Eu4Ga5SiAs9 and indicate ferromagnetism below T = 2 K.

scholarly journals Diffuse scattering from the lead-based relaxor ferroelectric PbMg1/3Ta2/3O3

2011 ◽  
Vol 44 (3) ◽  
pp. 603-609 ◽  
Author(s):  
Antonio Cervellino ◽  
S. N. Gvasaliya ◽  
O. Zaharko ◽  
B. Roessli ◽  
G. M. Rotaru ◽  
...  
Keyword(s):  
Single Crystal ◽  
Atomic Structure ◽  
Diffuse Scattering ◽  
Relaxor Ferroelectric ◽  
The Other ◽  
X Ray Diffraction ◽  
Correlation Lengths ◽  
X Ray ◽  
Displacement Vectors ◽  
Polar Nanoregions

The relaxor ferroelectric PbMg1/3Ta2/3O3was studied by single-crystal neutron and synchrotron X-ray diffraction, and its detailed atomic structure modelled in terms of static Pb displacements that lead to the formation of polar nanoregions. Similar to the other members of the Pb-based relaxor family like PbMg1/3Nb2/3O3or PbZn1/3Nb2/3O3the diffuse scattering in the [H00]/[0K0] scattering plane has a butterfly shape around theh00 Bragg reflections and is orthogonal to the scattering vector forhh0 peaks. In the [HH0]/[00L] plane the diffuse scattering is elongated along the 〈112〉 directions and is orthogonal to the scattering vector forhhhreflections. It is found that a model consisting of correlated Pb displacements along the 〈111〉 directions reproduces adequately the main features of the diffuse scattering in PbMg1/3Ta2/3O3when the correlation lengths between the Pb-ion displacement vectors are longest along the 〈111〉 and shortest along the 〈11{\overline 2}〉 and 〈1{\overline 1}0〉 directions.

Temperature dependence of the AV3O7 (A = Ca, Sr) structure

2007 ◽  
Vol 63 (6) ◽  
pp. 836-842 ◽  
Author(s):  
Sebastian Prinz ◽  
Karine M. Sparta ◽  
Georg Roth
Keyword(s):  
Single Crystal ◽  
Temperature Dependence ◽  
Crystal Structures ◽  
Room Temperature ◽  
X Ray Diffraction ◽  
X Ray ◽  
Space Groups ◽  
Temperature Ranges ◽  
First Time

The V4+ (spin ½) oxovanadates AV3O7 (A = Ca, Sr) were synthesized and studied by means of single-crystal X-ray diffraction. The room-temperature structures of both compounds are orthorhombic and their respective space groups are Pnma and Pmmn. The previously assumed structure of SrV3O7 has been revised and the temperature dependence of both crystal structures in the temperature ranges 297–100 K and 315–100 K, respectively, is discussed for the first time.

X-RAY DIFFRACTION STUDY OF THE MODULATED STRUCTURE IN SUPERCONDUCTING SINGLE-CRYSTAL Bi2Sr2CaCu2Oy

1988 ◽  
Vol 02 (08) ◽  
pp. 985-991 ◽  
Author(s):  
X. CHU ◽  
Z.H. MAI ◽  
Y.F. YAN ◽  
J.H. WANG ◽  
D.N. ZHENG ◽  
...  
Keyword(s):  
Experimental Data ◽  
Single Crystal ◽  
Diffraction Study ◽  
Basic Structure ◽  
X Ray Diffraction ◽  
Modulated Structure ◽  
Space Group ◽  
One Dimensional ◽  
X Ray ◽  
Average Structure

X-ray precession technique1 has been utilized to study the reciprocal space of the superconducting single crystal Bi 2 Sr 2 CaCu 2 O y. An average structure with space group of Pnnn and a real structure with the superspace group of [Formula: see text] or [Formula: see text] have been found for this one dimensional modulated incommensurate material. As well, a basic structure with the space group of Fmmm is derived from the experimental data.

scholarly journals Different Polyoxometalate Structures Obtained from the Na11H[H(2-x)Bi2W20O70(HWO3)x]·46H2O(x=1.4).

2018 ◽  
Vol 1 (2) ◽  
pp. 93-100
Author(s):  
Suhair Atta
Keyword(s):  
Single Crystal ◽  
Self Assembly ◽  
Multiple Testing ◽  
X Ray Diffraction ◽  
Triclinic Space Group ◽  
X Ray ◽  
Space Groups ◽  
Cell Parameters ◽  
New Family ◽  
Ft Ir

In the supramolecular chemistry world, Polyoxometalates (POMs) are considered as a new family of inorganic molecular containers, construct itself by self-assembly reaction from very small units, to form a cluster with unique structural and properties. three structures reported in this paper - differ in their unit cell parameters and also differ from the well-known - as the result of reaction of the Na11H[H(2- x)Bi2W20O70(HWO3)x]·46H2O (x=1.4) with Ca ion at different pH conditions. These structures are [Ca(H2O)7]2[Na(H2O)2]2[HBi2W20O70(HWO3)].14H2O(1), H2[NH4]10[HBi2W20O70(HWO3)] (2), and [NH4]6[Na(H2O)4]2[Ca(H2O)4]2[W12O42].2H2O (3). The last one is bismuth-free and it is formed through reassembly of the precursor. Full structural characterization was made by multiple testing techniques such as single-crystal X-ray diffraction, UV-visible spectroscopy, FT-IR, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). The single-crystal X-ray diffraction results for the three compounds are as follows:(1), Triclinic, space group P-1, while (2) and (3) crystallize in monoclinic space groups C2/m and P21/n respectively.

Structure of KNbOB2O5 – a commensurately modulated structure

2005 ◽  
Vol 61 (4) ◽  
pp. 361-366 ◽  
Author(s):  
Siegbert Schmid ◽  
Trixie Wagner
Keyword(s):  
Single Crystal ◽  
Diffraction Data ◽  
Group Symmetry ◽  
X Ray Diffraction ◽  
Modulated Structure ◽  
Space Group ◽  
X Ray ◽  
Average Structure ◽  
Modulated Structures ◽  
First Time

Members of the AMOB2O5 (A = K, Rb, Cs, Tl; M = Nb, Ta) family of compounds can be described as modulated structures with a single superspace group and very similar modulation functions. Single-crystal X-ray diffraction data (Mo Kα radiation) are used to solve and refine the structure of KNbOB2O5 in these terms for the first time. The average structure is solved and refined in the space group Pmn21. Subsequently, the atomic modulation functions are determined using JANA2000 and superspace-group symmetry Pmn21(0,0.375,0)s. The commensurately modulated structure is finally refined as a superstructure in the space group Pbn21 using SHELXS97 converging to R 1 = 0.024.

On the completeness of the β→ω transformation in metastable β titanium alloys

2017 ◽  
Vol 50 (1) ◽  
pp. 283-287 ◽  
Author(s):  
Jana Šmilauerová ◽  
Petr Harcuba ◽  
Dominik Kriegner ◽  
Václav Holý
Keyword(s):  
Single Crystal ◽  
Titanium Alloys ◽  
Radial Profile ◽  
Diffraction Maximum ◽  
X Ray Diffraction ◽  
X Ray ◽  
Β Phase ◽  
Ω Phase ◽  
Diffraction Peaks ◽  
Integrated Intensities

The completeness of the β→ω transformation in ω particles in a Ti–8 at.%Mo (Ti–15 wt%Mo) single crystal was investigated by measuring the X-ray diffraction maximum 20{\overline 2}2, which is forbidden in both the pure body-centred cubic β phase and the hexagonal ω phase, and also the diffraction maxima 0001, 0002 and 10{\overline 1}1, which are forbidden in the β phase and allowed in ω. From a comparison of the integrated intensities and widths of the diffraction peaks with simulations, the effective (mean) degree of the transformation was determined and the radial profile of the transformation degree in an ω particle was estimated.

Determination of single-crystal elasticity constants in a cubic phase within a multiphase alloy: X-ray diffraction measurements and inverse-scale transition modelling

2005 ◽  
Vol 38 (1) ◽  
pp. 30-37 ◽  
Author(s):  
S. Fréour ◽  
D. Gloaguen ◽  
M. François ◽  
A. Perronnet ◽  
R. Guillén
Keyword(s):  
Single Crystal ◽  
Elasticity Tensor ◽  
Cubic Phase ◽  
X Ray Diffraction ◽  
Two Phase ◽  
X Ray ◽  
Β Phase ◽  
Consistent Model ◽  
Transition Modelling

The scope of this work is the determination of single-crystal elastic properties from X-ray diffraction stress analysis performed on multiphase polycrystals. An explicit three-scale multiphase inverse self-consistent model is developed in order to express the single-crystal elasticity constants of a cubic phase as a function of its X-ray elasticity constants. The model is verified in the case of single-phase materials. Finally, it is applied to a two-phase (α+β) titanium-based alloy (Ti-17) and, as a result, the Ti-17 β-phase single-crystal elasticity tensor is estimated.

An analysis of recent single crystal X-ray diffraction measurements on calcium fluoride

1970 ◽  
Vol 26 (2) ◽  
pp. 208-214 ◽  
Author(s):  
M. J. Cooper
Keyword(s):  
Single Crystal ◽  
Calcium Fluoride ◽  
Diffuse Scattering ◽  
X Ray Diffraction ◽  
Poor Agreement ◽  
Thermal Diffuse Scattering ◽  
X Ray ◽  
Thermal Vibrations ◽  
Thermal Diffuse ◽  
Better Than

An analysis of recent single-crystal X-ray diffraction measurements on calcium fluoride has been carried out by comparing the observed data with those calculated from a theoretical model. A computer program was used which can refine parameters for extinction and anharmonic thermal vibrations in addition to the conventional parameters. It is shown that for the majority of the experiments in the recent ACA project the angle-dependent deviations between the experiments are consistent with those which would be expected due to a variation in the measured contributions from thermal diffuse scattering. There are discrepancies between experiments for the strongest reflexions, presumably because of errors associated with the use of attenuators, but if these reflexions are excluded the agreement between experiments, allowing for variations in the thermal diffuse scattering contributions, is much better than was indicated by previous analyses. The two remaining experiments and that reported by Zachariasen are in poor agreement with the others and this is attributed to the techniques used, namely an ω-scan with balanced filters in one case and a stationary-crystal, stationary-detector technique in the other two. Although the effects of anharmonicity on the X-ray intensities are rather small, the data from all experiments are consistent with the magnitude of an anharmonic thermal-vibration parameter, associated with the fluorine atoms, derived from neutron-diffraction measurements.

Structural characterization of RE10W22O81 rare-earth tungstates (RE = Ce, Nd)

2008 ◽  
Vol 64 (6) ◽  
pp. 708-712 ◽  
Author(s):  
Rosemary S. Barker ◽  
Ivana Radosavljevic Evans
Keyword(s):  
Rare Earth ◽  
Single Crystal ◽  
Diffraction Study ◽  
General Formula ◽  
Structural Characterization ◽  
X Ray Diffraction ◽  
Single Crystal Diffraction ◽  
X Ray ◽  
Space Groups

The single-crystal diffraction study of Ce10W22O81 and powder X-ray diffraction (XRD) experiments on Ce10W22O81 and Nd10W22O81 show that the true space group of these phases is Pbnm, contrary to the previous literature reports of the space groups Pbcn and Pbcm for the rare-earth tungstates (RE = La, Ce, Pr, Nd) with this general formula. The structure contains rare-earth cations in seven-, eight- and ninefold coordination. W atoms are found in corner-sharing WO5 groups, and also in WO6 and WO7 polyhedra which share edges and corners to form W6O17 units. The new model obtained from our single-crystal work gives better agreement with powder XRD data on both Ce10W22O81 and Nd10W22O81, and gives more plausible coordination environments and bond-valence sums.

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