scholarly journals The crystal structures and powder diffraction patterns of the uranium tellurides

1990 ◽  
Author(s):  
R.L. Snyder ◽  
M.C. Nichols ◽  
D.R. Boehme
Keyword(s):  
Crystal Structures ◽  
Powder Diffraction ◽  
Diffraction Patterns

The Crystal Structures and Powder Diffraction Patterns of the Uranium Tellurides: A Critical Review

1991 ◽  
Vol 6 (4) ◽  
pp. 204-227 ◽  
Author(s):  
Robert L. Snyder ◽  
Monte C. Nichols ◽  
Dale R. Boehme
Keyword(s):  
Crystal Structures ◽  
Powder Diffraction ◽  
Critical Review ◽  
Poor Quality ◽  
Diffraction Patterns

AbstractA critical review of all the reported structures and powder diffraction patterns in the uranium telluride system has been undertaken. Our recommendations are:1. Structures that are correct:• Cubic – UTe: no experimental pattern exists. Retain calculated 15–865.• Cubic – U3Te4: retain poor quality 12-610 but adopt the pattern calculated here.• Cubic U2Te3: no experimental pattern exists. Adopt pattern calculated here.• Orthorhombic UTe2: Adopt the new pattern of Boehme et al.• Monoclinic αUTe3: Adopt the new pattern of Boehme et al.• Orthorhombic βUTe3: Adopt the pattern calculated here.• Orthorhombic UTe5: Adopt the new pattern of Boeheme et al.2. Structures in need of refinement:• Orthorhombic U2Te3: Adopt pattern calculated here over 34-807.• Hexagonal U7Te12: Adopt pattern calculated here but retain 24-1368.• Orthorhombic UTe1.78: Adopt pattern calculated here and retain our modified 21-1404 reported for U4Te7.• Orthorhombic UTe2.5: Adopt pattern calculated here.• Orthorhombic UTe3.4: Accept recent pattern of Boehme et al.3. Phases for which no structures or reliable patterns exist:• Orthorhombic U3Te4: no published pattern.• Tetragonal U3Te5: three patterns 21-1407, 34-766 and 34-896 exist but all are of very poor quality.4. Phases which probably do not exist:• Tetragonal UTe1.77• Tetragonal UTe2• Cubic UTe2• U3Te7 (21-1402)• U3Te8 (21-1406)

Identification of the Polytype-like Modifications of Ca3GeO5 by Powder Diffraction

1986 ◽  
Vol 1 (1) ◽  
pp. 44-49
Author(s):  
Yoshio Takeuchi ◽  
Fumito Nishi
Keyword(s):  
Diffraction Pattern ◽  
Crystal Structures ◽  
Powder Diffraction ◽  
Synthetic Product ◽  
Diffraction Patterns

AbstractFeatures of the powder diffraction patterns of known polytype-like modifications of Ca3GeO5, such as 2H, 9R and 24R types, and a monoclinic polymorph have been studied by means of the patterns calculated based on their crystal structures. The result has provided keys to identify them when they coexist in the same synthetic product. Accounts have been given on the crystallographic features of the building layer and rules for layer stackings of the modifications in general. Any modification may then be constructed to predict its powder diffraction pattern.

scholarly journals Data Validation and Structural Classifications in Powder Diffraction File

2014 ◽  
Vol 70 (a1) ◽  
pp. C1702-C1702
Author(s):  
Soorya Kabekkodu
Keyword(s):  
Crystal Structures ◽  
Powder Diffraction ◽  
Pattern Search ◽  
Published Data ◽  
Powder Diffraction File ◽  
Recent Developments ◽  
Diffraction Patterns ◽  
Quality Mark ◽  
Editorial Review

The new Powder Diffraction File™, housing more than 760,000 diffraction patterns and 200,000 crystal structures, has a wealth of information that a materials scientist can take advantage of in various ways, from materials identification, characterization to design. Various structural and chemical classifications implemented in the database will be presented in detail. These classifications are important in data mining studies and optimizing pattern search/match methods. While using any database in materials characterization, it is important to know the quality of the crystal structure or diffraction pattern found in the database. With varying quality of published data in the literature, database editorial review processes had to adopt rigorous data evaluation methods to classify data based on its quality. Every entry in the Powder Diffraction File™ has a quality mark and editorial comments describing the error and the correction. Results of the analysis of the quality of the crystal structures (~500,000) published over the years will be discussed along with the most common errors found. The recent developments in Powder Diffraction File will be presented.

Structures and X-ray diffraction patterns of compounds in the Sr–Nd–Cu–O system

1995 ◽  
Vol 10 (1) ◽  
pp. 56-66 ◽  
Author(s):  
Winnie Wong-Ng
Keyword(s):  
Crystal Structures ◽  
Powder Diffraction ◽  
X Ray Diffraction ◽  
Powder Diffraction File ◽  
Comprehensive Review ◽  
X Ray ◽  
Diffraction Patterns ◽  
Ternary Oxides

A comprehensive review of phases found in the Sr–Nd–Cu–O system which contains the high Tc superconductor phase Sr1−xNdxCuO2 has been prepared. This paper summarizes the crystal structures reported in the literature and the X-ray powder diffraction patterns reported in the ICDD Powder Diffraction File (PDF). In order to supplement the PDF with new patterns, calculated X-ray powder diffraction patterns generated from reported structures are provided for five ternary oxides: Sr0.86Nd0.14CuO2, SrNdCuO3.5, Sr6Nd3Cu6O17, Sr2NdCu2O5.66, and Sr1.2Nd1.8Cu2O6.

Pyrochlores. VIII. Studies of some 2–5 Pyrochlores and Related Compounds and Minerals

1972 ◽  
Vol 50 (22) ◽  
pp. 3648-3666 ◽  
Author(s):  
François Brisse ◽  
David J. Stewart ◽  
V. Seidl ◽  
Osvald Knop
Keyword(s):  
Crystal Structures ◽  
Crystal Chemistry ◽  
Powder Diffraction ◽  
Mixed Crystals ◽  
Powder Diffractometer ◽  
Pyrochlore Type ◽  
Diffraction Patterns ◽  
Relationship Of ◽  
The Relationship ◽  
Related Compounds

The cubic pyrochlores Cd2Nb2O7, Cd2Ta2O7, Sn2Nb2O7, Sn2Ta2O7. Cd2Sb7O7, Ca2Sb2O7, Mn2Sb2O7, Pb2Sb2O7, and related compounds were prepared and investigated by a number of methods. On heating above 700°. Ca2Sb2O7(pyrochlore) transformed to Ca2Sb2O7(weberite), while Pb2Sb2O7(pyrochlore) changed to a rhombohedrally distorted Pb2Sb2O7 pyrochlore. Refinement of the crystal structures of Cd2Nb2O7 and Cd2Ta2O7 from powder diffractometer intensities yielded 0.434(2) and 0.434(3) respectively as the best estimates of x(O2). Specimens of natural bindheimite and stibiconite were also examined. Stibiconite from San Luis Potosi (Mexico) was shown, on the evidence of its Mössbauer 121Sb spectrum, to contain Sb(V) and Sb(III) in the approximate ratio of 0.2.BaCd2Cl6•5H2O and BaCd2Cl6•2H2O both give powder diffraction patterns of the pyrochlore type. The chlorine could be partially replaced by Br to give mixed crystals BaCd2Cl6−zBrz•5H2O almost up to z = 2.The crystal chemistry of 2–5 oxide pyrochlores and the relationship of the weberite to the pyrochlore phases are discussed.

Improved powder diffraction patterns for the titanium suboxides TinO2n−1 (4≤n≤9)

1996 ◽  
Vol 11 (1) ◽  
pp. 60-68 ◽  
Author(s):  
M. E. Bowden ◽  
G. V. White ◽  
I. W. M. Brown ◽  
M. J. Ryan ◽  
G. J. Gainsford
Keyword(s):  
Experimental Data ◽  
Thermodynamic Properties ◽  
Single Crystal ◽  
Crystal Structures ◽  
Powder Diffraction ◽  
Single Phase ◽  
Powder Xrd ◽  
Single Crystal Structures ◽  
Diffraction Patterns ◽  
Xrd Patterns

Improved powder XRD patterns for the titanium suboxides, TinO2n−1 (4≤n≤9), have been calculated from published single-crystal structures. To provide the best match with experimental data, the entire diffraction traces were simulated, and d-spacings and intensities extracted in the same manner as from experimental traces. The accuracy of the new patterns has been verified by comparison with measured powder patterns, particularly in the case of the n=4 and n=5 compounds where single-phase powders can be prepared relatively easily. Difficulties experienced preparing higher homologues have been related to the thermodynamic properties of this system.

Searching the Cambridge Structural Database for polymorphs

2005 ◽  
Vol 61 (5) ◽  
pp. 504-510 ◽  
Author(s):  
Jacco van de Streek ◽  
Sam Motherwell
Keyword(s):  
Crystal Structures ◽  
Powder Diffraction ◽  
Chemical Compound ◽  
Unit Cell ◽  
Cambridge Structural Database ◽  
Structural Database ◽  
Diffraction Patterns ◽  
Cell Volumes

In order to identify all pairs of polymorphs in the Cambridge Structural Database (CSD), a method was devised to automatically compare two crystal structures. The comparison is based on simulated powder diffraction patterns, but with special provisions to deal with differences in unit-cell volumes caused by temperature or pressure. Among the 325 000 crystal structures in the Cambridge Structural Database, 35 000 pairs of crystal structures of the same chemical compound were identified and compared. A total of 7300 pairs of polymorphs were identified, of which 154 previously were unknown.

Crystal structures and reference X-ray powder diffraction patterns of Sr4−xCaxPb2O8 (x=1,2,3)

1998 ◽  
Vol 13 (4) ◽  
pp. 232-240 ◽  
Author(s):  
W. Wong-Ng ◽  
J. A. Kaduk ◽  
W. Greenwood
Keyword(s):  
Crystal Structure ◽  
Solid Solution ◽  
Crystal Structures ◽  
Powder Diffraction ◽  
Alkaline Earth ◽  
Lattice Parameters ◽  
X Ray Diffraction ◽  
Powder Diffraction File ◽  
X Ray ◽  
Diffraction Patterns

The crystal structure of the solid solution alkaline earth plumbate phase Sr4−xCaxPb2O8 was investigated using the X-ray Rietveld technique for x=1, 2, and 3. The lattice parameters a, b, c, and V were found to decrease linearly as the Sr at site 4h was replaced by Ca. The structure features chains of edge-sharing PbO6 octahedra, linked by seven-coordinated (Ca/Sr)–O monocapped trigonal prisms. The structure is similar to that of Pb3O4, which can be reformulated as Pb2IIPbIVO4. X-ray diffraction patterns for the solid solution members SrCa3Pb2O8, Sr2Ca2Pb2O8, and Sr3CaPb2O8 were prepared for inclusion in the Powder Diffraction File.

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