Crystal structure determination of lithium diborate hydrate, LiB2O3(OH).H2O, from X-ray powder diffraction data collected with a curved position-sensitive detector

1992 ◽  
Vol 25 (5) ◽  
pp. 617-623 ◽  
Author(s):  
D. Louër ◽  
M. Louër ◽  
M. Touboul
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Structural Model ◽  
Rietveld Method ◽  
Position Sensitive Detector ◽  
X Rays ◽  
Sensitive Detector ◽  
Powder Diffraction Data ◽  
Position Sensitive

The crystal structure of lithium diborate hydrate, LiB2O3(OH).H2O, has been solved ab initio and refined by the Rietveld method from powder diffraction data collected with a curved position-sensitive detector (INEL CPS120) using Debye–Scherrer diffraction geometry with monochromatic X-rays. In the first stage the indexing of the powder pattern was performed by the successive dichotomy method from data collected with a diffractometer using Bragg–Brentano geometry. The lattice parameters are a = 9.7984 (10), b = 8.2759 (7) and c = 9.6138 (8) Å and the space group is Pnna. The structural model was obtained from direct methods and two difference Fourier maps. The Rietveld refinement converged to final crystal structure and profile indicators RF = 0.05, RB = 0.05, Rp = 0.03 and Rwp = 0.04. The structure consists of BO4 tetrahedra (T) and BO2(OH) triangles (Δ) sharing corners in order to form infinite chains along [010], with the shorthand notation 3:∞1(Δ + 2T). The particular linkage of the B3O3 rings leads to a new diborate anion {[B2O3(OH)] n− n }, in which two tetrahedral B atoms have an occupation factor of 0.5. Li atoms, tetrahedrally surrounded by four O atoms, three belonging to separate chains and one to a water molecule maintain the cohesion of the structure.

Rietveld Structure Refinement of the Apophyllite Crystals from Deccan Basalt Plateau Using X-ray Powder Diffraction Data

2020 ◽  
Vol 70 (12) ◽  
pp. 4248-4254
Keyword(s):  
Crystal Structure ◽  
Rietveld Refinement ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Method ◽  
X Rays ◽  
Powder Diffraction Data ◽  
Deccan Basalt ◽  
X Ray ◽  
Basalt Plateau

The crystal structure of a rare sample of natroapophyllite from Pune district (western India) located in the Deccan Basalt Plateau has been refined using X-Ray powder diffraction data and the Rietveld method. The Rietveld refinement was carried out using the computer program Diffracplus TOPAS 4.1. The pseudo-Voigt (pV) profile function was used for the fit of the peaks. The Rietveld refinement of the analyzed sample in space group Pnnm (No.58): a=8.94771 Å, b=8.98013 Å, c=15.78878 Å, Z=2, confirm the basic natroapophyllite structure. The chemical composition of the apophyllite crystals from Pune region (India) was determined by EDX analysis. The paper presents a new set of the unit cell parameters and fractional coordinates that define the natroapophyllite crystal structure. The quality of the sample analyzed was pristine, the sample being collected from an association of apophyllite-stilbite crystals of centimetric dimensions. Keywords: natroapophyllite, crystal structure, X-rays diffraction, EDX, Rietveld method

Crystallographic study of ternary ordered skutterudite IrGe1.5Se1.5

2010 ◽  
Vol 25 (3) ◽  
pp. 247-252 ◽  
Author(s):  
F. Laufek ◽  
J. Návrátil
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Method ◽  
Crystallographic Data ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Crystallographic Study ◽  
Related Phase ◽  
The Ideal

The crystal structure of skutterudite-related phase IrGe1.5Se1.5 has been refined by the Rietveld method from laboratory X-ray powder diffraction data. Refined crystallographic data for IrGe1.5Se1.5 are a=12.0890(2) Å, c=14.8796(3) Å, V=1883.23(6) Å3, space group R3 (No. 148), Z=24, and Dc=8.87 g/cm3. Its crystal structure can be derived from the ideal skutterudite structure (CoAs3), where Se and Ge atoms are ordered in layers perpendicular to the [111] direction of the original skutterudite cell. Weak distortions of the anion and cation sublattices were also observed.

The crystal structure of sarmientite, Fe23+ (AsO4)(SO4)(OH)·5H2O, solved ab initio from laboratory powder diffraction data

2014 ◽  
Vol 78 (2) ◽  
pp. 347-360 ◽  
Author(s):  
F. Colombo ◽  
J. Rius ◽  
O. Vallcorba ◽  
E. V. Pannunzio Miner
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Method ◽  
Direct Methods ◽  
Hydroxyl Group ◽  
Monoclinic Space Group ◽  
Powder Diffraction Data ◽  
Patterson Function ◽  
Unit Cell Dimensions

AbstractThe crystal structure of sarmientite, Fe23+ (AsO4)(SO4)(OH)·5H2O, from the type locality (Santa Elena mine, San Juan Province, Argentina), was solved and refined from in-house powder diffraction data (CuKα1,2 radiation). It is monoclinic, space group P21/n, with unit-cell dimensions a = 6.5298(1), b = 18.5228(4), c = 9.6344(3) Å, β = 97.444(2)º, V = 1155.5(5) Å3, and Z = 4. The structure model was derived from cluster-based Patterson-function direct methods and refined by means of the Rietveld method to Rwp = 0.0733 (X2 = 2.20). The structure consists of pairs of octahedral-tetrahedral (Fe−As) chains at (y,z) = (0,0) and (½,½), running along a. There are two symmetry-independent octahedral Fe sites. The Fe1 octahedra share two corners with the neighbouring arsenate groups. Both individual chains are related by a symmetry centre and joined by two symmetry-related Fe2 octahedra. Each Fe2 octahedron shares three corners with double-chain polyhedra (O3, O4 with arsenate groups; the O8 hydroxyl group with the Fe1 octahedron) and one corner (O11) with the monodentate sulfate group. The coordination of the Fe2 octahedron is completed by two H2O molecules (O9 and O10). There is also a complex network of H bonds that connects polyhedra within and among chains. Raman and infrared spectra show that (SO4)2− tetrahedra are strongly distorted.

Powder diffraction data of two tricydic diazonia diiodide salts used in silver iodide solid electrolytes

1993 ◽  
Vol 8 (3) ◽  
pp. 175-179
Author(s):  
J. Estienne ◽  
O. Cerclier ◽  
J. J. Rosenberg
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Silver Iodide ◽  
Solid Electrolytes ◽  
Rietveld Method ◽  
Powder Diffraction Data ◽  
Organic Salts ◽  
X Ray ◽  
Structure Determinations

Indexed X-ray powder diffraction data are reported for two organic salts with carbon rings having two quaternary nitrogens: diazonia-6,9 dispiro [5.2.5.2] hexadecane and diazonia-6,9 dispiro [5.2.5.3] heptadecane diiodides. For these compounds, which give solid electrolytes when associated with AgI, powder diffraction diagrams calculated by the Rietveld method from single crystal structure determinations are presented and are compared to the experimental diffraction data.

Cristobalite-Related Phases in the NaAlO2–NaAlSiO4 System. II. A Commensurately Modulated Cubic Structure

1998 ◽  
Vol 54 (5) ◽  
pp. 547-557 ◽  
Author(s):  
R. L. Withers ◽  
J. G. Thompson ◽  
A. Melnitchenko ◽  
S. R. Palethorpe
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Method ◽  
Powder Diffraction Data ◽  
Tetrahedral Framework ◽  
X Ray ◽  
Sodium Aluminosilicate ◽  
Vacancy Ordering ◽  
Cubic Structure

The crystal structure of a new cubic cristobalite-related sodium aluminosilicate Na1.45Al1.45Si0.55O4 [P213, a = 14.553 (1) Å] has been modelled using a modulation wave approach and the model tested against X-ray powder diffraction data using the Rietveld method. Owing to there being 64 independent positional parameters and eight independent Na sites, refinement of the tetrahedral framework atom positions and Na occupancies was not possible. The framework was modelled successfully in terms of q 1 = 1\over 4〈020〉_p^*-type (p = parent) modulation waves with the requirement that the MO4 (M = Al0.725Si0.275) tetrahedra be as close to regular as possible. Na/vacancy ordering was modelled successfully in terms of q 2 = 1\over 4〈220〉_p^* modulation waves. Only the Na-atom positions were refined. The significance of this unique modulated cubic cristobalite-related structure and the possible insight it provides to understanding β-cristobalite are discussed.

The crystal structure of perdeuterated methanol monoammoniate (CD3OD·ND3) determined from neutron powder diffraction data at 4.2 and 180 K

2009 ◽  
Vol 42 (6) ◽  
pp. 1054-1061 ◽  
Author(s):  
A. D. Fortes ◽  
I. G. Wood ◽  
K. S. Knight
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Method ◽  
Neutron Powder Diffraction ◽  
Relative Volume ◽  
Powder Diffraction Data ◽  
Orthorhombic Space Group ◽  
Neutron Powder Diffraction Data

The crystal structure of perdeuterated methanol monoammoniate, CD3OD·ND3, has been solved from neutron powder diffraction data collected at 4.2 and 180 K. The crystal structure is orthorhombic, space groupPbca(Z= 8), with unit-cell dimensionsa= 11.02320 (7),b= 7.66074 (6),c= 7.59129 (6) Å,V= 641.053 (5) Å3[ρcalc= 1162.782 (9) kg m−3] at 4.2 K, anda= 11.21169 (5),b= 7.74663 (4),c= 7.68077 (5) Å,V= 667.097 (4) Å3[ρcalc= 1117.386 (7) kg m−3] at 180 K. The crystal structure was determined byab initiomethods from the powder data; atomic coordinates and anisotropic displacement parameters were subsequently refined by the Rietveld method toRp< 3% at both temperatures. The crystal comprises a sheet-like structure in thebccrystallographic plane, consisting of strongly hydrogen bonded elements; these sheets are stacked along theaaxis, and adjacent sheets are linked by what may be comparatively weak C—D...O hydrogen bonds. Within the strongly bonded sheet structure, ND3molecules are tetrahedrally coordinated by the hydroxy moieties of the methanol molecule, accepting one hydrogen bond (O—D...N) of length ∼1.75 Å, and donating three hydrogen bonds (N—D...O) of length 2.15–2.25 Å. Two of the methyl deuterons appear to participate in weak interlayer hydrogen bonds (C—D...O) of length 2.7–2.8 Å. The hydrogen bonds are ordered at both 4.2 and 180 K. The relative volume change on warming from 4.2 to 180 K, ΔV/V, is +4.06%, which is comparable to, but more nearly isotropic (as determined from the relative change in axial lengths,e.g.Δa/a) than, that observed in deuterated methanol monohydrate.

Crystal Structure of La4Si2O7N2Analyzed by the Rietveld Method Using the Time-of-Flight Neutron Powder Diffraction Data

2003 ◽  
Vol 15 (5) ◽  
pp. 1099-1104 ◽  
Author(s):  
Junichi Takahashi ◽  
Hisanori Yamane ◽  
Naoto Hirosaki ◽  
Yoshinobu Yamamoto ◽  
Takayuki Suehiro ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Method ◽  
Time Of Flight ◽  
Neutron Powder Diffraction ◽  
Powder Diffraction Data ◽  
Neutron Powder Diffraction Data

Refinement of the Structure of MnSi by Powder Diffraction

1991 ◽  
Vol 6 (4) ◽  
pp. 194-195 ◽  
Author(s):  
Jens-Erik Jørgensen ◽  
Svend Erik Rasmussen
Keyword(s):  
Lattice Constant ◽  
Powder Diffraction ◽  
Rietveld Method ◽  
Internal Standard ◽  
Position Sensitive Detector ◽  
Intensity Data ◽  
Sensitive Detector ◽  
Crystal Data ◽  
Position Sensitive

AbstractCrystal data and results of structure refinements for MnSi are reported. The material is cubic, P213, with a = 4.5603(2) Å, Vd = 94.84(1) Å3, Z = 4, Dx = 5.815 Mg/m3. Intensity data were obtained from a Stoe transmission type diffractometer equipped with a position sensitive detector. CuKα1 radiation, λ = 1.5405981 Å was employed. Germanium was used as an internal standard for the determination of the lattice constant (aGe= 5.6582 Å). The structure was refined by the Rietveld method by aid of three different programs.

Solving the Crystal Structure of Cd5(OH)8(NO3)2·2H2O from Powder Diffraction Data. A Comparison with Single Crystal Data

1991 ◽  
Vol 6 (1) ◽  
pp. 10-15 ◽  
Author(s):  
Patricia Bénard ◽  
Michèle Louër ◽  
Daniel Louër
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Method ◽  
Subsequent Treatment ◽  
Crystal Data ◽  
Powder Diffraction Data ◽  
Indexing Method ◽  
Parameter Values

AbstractA comparison between the results of ab initio structure determination from X-ray powder diffraction data of a new cadmium hydroxide nitrate, Cd5(OH)8 (NO3)2·2H2O (SG C2/m), and those obtained from single crystal data is presented. The powder diffraction pattern has been analysed by an indexing method and fitting techniques. A total of 119 unambiguously indexed reflections has been extracted and used in subsequent treatment. The power of powder techniques to index the pattern and to find the structure model by normal Patterson and Fourier methods is clearly shown. The refinement of approximate coordinates has been carried out by the Rietveld method (444 reflections). The comparison of results with those obtained from single crystal data (2218 reflections) shows that the precision of positional parameter values is lower by a factor of 10, on average, in the powder study. These results are discussed in terms of crystallographic parameters (number of reflections used, number of parameters to refine, contrast between atoms) and, also, in terms of sample dependent properties (preferred orientation effect, impurity). Finally, the crystal structure has been derived from powder data with a precision probably sufficient for most purposes.

scholarly journals Structures of FeII spin-crossover complexes from synchrotron powder-diffraction data

2004 ◽  
Vol 60 (5) ◽  
pp. 528-538 ◽  
Author(s):  
Eva Dova ◽  
René Peschar ◽  
Makoto Sakata ◽  
Kenichi Kato ◽  
Arno F. Stassen ◽  
...  
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Structure Determination ◽  
Structural Changes ◽  
Spin Crossover ◽  
Structural Model ◽  
Rietveld Method ◽  
Space Structure ◽  
Powder Diffraction Data ◽  
Synchrotron Powder Diffraction

Crystal structure determination and analysis have been carried out for the two spin-crossover compounds [Fe(teeX)6](BF4)2 (teeX is haloethyltetrazole; X = I: teei; X = Br: teeb), in both their high-spin (near 300 K) and their low-spin states (T = 90 K), using high-resolution powder-diffraction data collected at the ESRF (Grenoble, France) and SPring8 (Japan) synchrotron radiation facilities. The structures of teei have been solved using various direct-space structure determination techniques (grid search, genetic algorithm and parallel tempering) and refined with the Rietveld method using geometrical restraints. In the case of teeb, a structural model was found but a full refinement was not successful because of the presence of a significant amount of an amorphous component. Analysis of the structures (space group P21/c, Z = 2) and diffraction data, and the absence of phase transitions, show the overall structural similarity of these compounds and lead to the conclusion that the gradual spin-crossovers are likely to be accompanied by small structural changes only.

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