Neutron powder diffraction studies in CaMn1‐xCuxO3 (x = 0, 0.2)

Neutron powder diffraction patterns were recorded on CaMn_1‐xCu_xO₃ (x = 0 and 0.20) compounds at different temperatures down to 11K. All the patterns were analyzed by employing Rietveld refinement technique and using the Fullprof program. The observed crystallographic peaks could be refined by using Pbnm space group and no structural transition has been observed down to 11K. An additional peak at 2θ = 16.7° has been observed with decrease in temperature below T_N and its intensity was found to increase with decrease in temperature. It could be indexed to magnetic (101) plane. The magnetic ordering is found to be G‐type antiferromagnetic behaviour. The magnetic moment at 11K for the samples x = 0.0 and 0.20 are found to be 2.69 and 2.42μ_B. The doped Cu ions are found to be in Cu²⁺ state and take part antiferromagnetic interactions with Mn ions. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

X‐ray diffraction refinement of the crystal structure of anosovite prepared from leucoxene

The crystal structure of anosovite, (Ti_1.69Al_0.26Fe_0.05)³⁺(Ti_0.97Zr_0.03)⁴⁺O₅, prepared by carbothermal reduction of leucoxene under vacuum at 1450°C has been refined by Rietveld method using powder X‐ray diffraction data. It was found that it represents slightly monoclinically deformed pseudobrookite type structure with lattice parameters a = 9.8111 Å, b = 3.7509 Å, c = 9.9468 Å, β = 90.628°. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Structure refinement of cadmium cerium(IV) phosphate Cd<Subscript>0.5</Subscript>Ce<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript>

Cadmium cerium orthophosphate Cd_0.5Ce₂(PO₄)₃ is synthesized by precipitation from aqueous solutions. The structure refinement from powder X-ray diffraction data is preceded by the sample preparation and structure solution. The refinement is carried out by the Rietveld method (ADP-2 diffractometer, Cu _Kα radiation, Ni filter, 15° < 2θ < 120°, 2θ-scan step 0.02°, counting time 10 s per step). All calculations are carried out using the WYRIET program (version 3.3) within the sp. gr. P2₁/n. The structure is refined with anisotropic displacement parameters for cations and isotropic displacement parameters for oxygen atoms.     

Crystal structure refinement of the ternary compound Cu2SnTe3 by X‐ray powder diffraction

The ternary compound Cu₂SnTe₃ crystallizes in the Imm2 (Nº 44) space group, Z = 2, with a = 12.833(4) Å, b = 4.274(1) Å, c = 6.043(1) Å, V = 331.5(1) ų. Its structure was refined from X‐ray powder diffraction data using the Rietveld method. The refinement of 25 instrumental and structural variables led to R_p = 10.2%, R_wp = 11.8%, R_exp = 7.7%, R_B = 10.6%, S = 1.6 and χ² = 2.6, for 5501 step intensities and 163 independent reflections. This compound is isostructural with Cu₂GeSe₃, and consists of a three‐dimensional arrangement of slightly distorted CuTe₄ and SnTe₄ tetrahedra connected by common corners. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal Structure of (Cr,Cu)(Sr,La)2(La,A)Cu2O8‐δ (1212‐type) and (Cr,Cu)Sr2(Y,Ce)2Cu2O10‐δ (1222‐type) Phases

Conditions of the synthesis, crystal structures, mechanical properties, electrical resistivities and magnetizations of cuprates with the general formula (Cr,Cu)(Sr,La)₂(La,A)Cu₂O_8‐δ where A=Ca or Sr of 1212‐type and (Cr,Cu)Sr₂(Y,Ce)₂Cu₂O_10‐δ of 1222‐type were investigated. The compositions of the cuprates and an amount of the impurity phases in the samples were determined. Rietveld refinement of the structure was carried out. It was found that the formal charges of Cu (FC_Cu) calculated from the electroneutrality of refined phase compositions do not achieve value optimal for the appearence of superconducting phases.     

New phosphate Fe0.5Nb1.5(PO4)3 with an electrically neutral framework. Synthesis and crystal structure

A new iron-niobium phosphate, Fe_0.5Nb_1.5(PO₄)₃, has been prepared and studied by X-ray diffraction, electron microprobe analysis, IR spectroscopy, and neutron powder diffraction. On the basis of X-ray powder data, it was found that the synthesized phosphate crystallizes into the sp. gr. R $\bar 3$ c and corresponds to the structural type of sodium-zirconium phosphate NaZr₂(PO₄)₃. The structure was refined by the Rietveld method based on a powder neutron diffraction experiment. The obtained phosphate belongs to complex niobium orthophosphates and has a framework structure with a zero framework charge.     

Crystal structure analysis of Bis{(N,N′‐dimethylformamide)‐[μ‐bis‐N,N′‐(2‐oxybenzyl)‐1,3‐propanediaminato](μ‐asetato) nickel(II)}nickel(II)

The title compound, a homotrinuclear Ni^II complex has been synthesized from ONNO type Schiff base reduced with the help of NaBH₄. The structure of the complex, [Ni{Ni(CH₃CO₂) (C₁₇H₂₀N₂O₂) (C₃H₇NO)}₂], was identified using elemental analysis, thermal analysis, IR spectroscopy and x‐ray diffraction techniques. It was established that although some bond lengths and angles changed with respect to previous complexes, the Ni…Ni distance was approximately the same.     

X‐ray diffraction analysis of powder and thin film of (Gd1‐x Yx)2O3 prepared by sol‐gel process

The mixed oxide (Gd_1‐xY_x)₂O₃ (0.0 ≤ x ≤ 1.0) were synthesized, as powder and thin film, by a sol‐gel process. X‐ray diffraction data were collected and crystal structure and microstructure analysis were performed using Rietveld refinement method. All samples were found to have the same crystal system and formed solid solutions over the whole range of x. The cationic distribution, Gd³⁺ and Y³⁺, over the two non‐equivalent sites 8b and 24d of the space group Ia3 is found to be random for all values of (x). The lattice parameter is found to vary linearly with the composition (x). Replacing Gd³⁺ and Y³⁺ by each other introduces a systemic decrease in the x‐coordinate of cation position (24d) and slight changes in the oxygen coordinates. Crystallite size and microstrain analysis is performed along different crystallographic directions and anisotropic changes are found with the composition parameter (x). The average crystallite size ranges from 75 to 149 nm and the r.m.s strain from 0.027 to 0.068 x10^‐2. Textured Gd_1.841Y_0.159O₃ (400) buffer layers, with a high degree of alignment in both out‐plane and in‐plan, are successfully grown on cube textured Ni (001) tape substrates by sol–gel dip coating process. The resulting buffer layers are crack‐free, pinhole‐free, dense and smooth. YbBa₂Cu₃O_7‐x (YbBCO) thin film could be (00l) epitaxially grown on the obtained buffer layer using sol–gel dipping technique. (© 2007 WILEY ‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

High temperature powder diffraction and solid state DFT study of β‐cryolite (Na3AlF6)

Neutron and synchrotron powder diffraction data for β‐cryolite were collected within 550‐800(880) °C. Atomic coordinates of Al, F and Na atoms were obtained by both neutron Rietveld refinement and energy minimization in solid state at DFT level of theory. It was shown that although Rietveld refinements with fluorine atoms statically displaced from the 24e to the 96k special position of the Fm‐3m space group provide a reasonable fit to the experimental data, the refined structure differ from that obtained by the total energy minimization. The structure with the minimum of the total energy corresponds to the low temperature α‐phase with a zigzag arrangement of the polyhedra built around the Al and Na atoms. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The crystal structure of Zr2Se reinvestigated by electron crystallography and X-ray powder diffraction

The metal-rich compound Zr₂Se is of particular interest for electron crystallography, since it was one of the first examples that proved that heavy-atom structures can be solved via quasi-automatic direct methods from selected area electron diffraction intensities [1]. For this reason, Zr₂Se has been chosen as a model to discuss the possibilities and the limits of the quasi-kinematical approach that has been successfully used to determine this and related structures from high-resolution electron microscopy (HREM) images and selected area electron diffraction. In order to quantify the achievable accuracy of the electron crystallography techniques used, the corresponding structures are compared with results from structural analysis with X-ray powder data and with a model received from first-principles calculations. The latter structure was chosen in this study as a reference, since the calculations do not depend on experimental parameters. Analysis of the obtained result from electron diffraction structural analysis (EDSA) shows that the structural model is, on average, only off by 0.08 Å, despite the investigated crystal having an effective thickness of 286 Å. The corresponding result from Rietveld refinement with X-ray powder data agrees to within 0.04 Å with the structure from calculation and within 0.03 Å with the result from an earlier single crystal X-ray study [2].     

A Structural Study of Aluminate Sodalite Ca8[Al12O24](CrO4)2(CACr)

The structure of the cubic high temperature phase of Ca₈[Al₁₂O₂₄] (CrO₄)₂, CACr, has been determined at 700 K by Rietveld analysis of neutron powder diffraction data. The structure is discussed with respect of those of its homologues. The phase transitions of the title compound have been investigated by means of synchrotron x-ray powder diffraction and differential thermo analysis. High precision lattice parameters have been determined in the temperature range between 350 and 750 K. Three phase transitions occurring at 610 K, 453 K, and 432 K could be verified. Observed anomalies in the lattice parameters versus temperature might indicate a yet unknown phase transition at about 555 K. This is supported by results of differential thermo analysis.     

Crystal and molecular structure of trans‐(±)‐3‐acetoxy‐2‐(4‐methoxyphenyl)‐4‐oxo‐2,3,4,5‐tetrahydro‐1,5‐benzothiazepine‐1‐oxide

The title compound is a structurally related isomer of diltiazem, a well known drug. This compound (C₁₈H₁₇NO₅S) crystallizes in the space group P2₁/n with a = 13.803(4), b = 7.704(3), c = 16.093(3) Å, β = 105.37(2)º, Z = 4, V = 1650.1(9) ų. The least‐squares refinement gave residual index R = 0.067 for 2831 observed reflections. The distorted seven‐membered ring in the molecule shows twist‐boat conformation. Hydrogen bonds in which the amide group at one molecule and a carbonyl group in the adjacent molecule are involved to form centrosymmetric dimers in the crystal. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Refinement of the crystal structure of rhombohedral KU<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript> as a representative of orthophosphates with the NaZr<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript> structure

The crystal structure of the high-temperature β modification of synthetic orthophosphate KU₂(PO₄)₃ was refined from powder X-ray diffraction data by the Rietveld method: sp. gr. \(R\bar 3c\), the unit-cell parameters a= 9.113(1) Å and c= 24.997(1) Å. The isotropic refinement converged to R _wp = 6.15, R _B = 2.14, R _F = 3.52, and S = 0.42. It was confirmed that β-KU₂(PO₄)₃ belongs to the structure type of sodium zirconium phosphate containing an actinide atom in a sixfold (octahedral) coordination formed by oxygen atoms, which is unusual for orthophosphates. The principal interatomic distances and bond angles in the structure are reported.     

Structural studies of crystalline oligosaccharides VI: Crystal structure and conformation of benzyl‐4,6‐O‐benzylidene‐3‐O‐benzoyl‐β‐D‐galactoside

Monsaccharides are the building blocks of polysaccharides and hence are the simplest sugar molecules to study the conformation and molecular structures of sugars. Benzyl‐4,6‐O‐benzylidene‐3‐O‐benzoyl‐β‐D‐galactoside is a key intermediate in the synthesis of polysaccharides. Crystal structural investigation of the title compound was undertaken to establish their chemical structure as well as to study their solid state conformation. Crystals of the title compound, obtained from water/methanol, are orthorhombic, space group P2₁2₁2₁, with cell dimensions a=11.290 (4), b=9.941 (1), c= 21.442(2)Å, V= 2406ų, Z=4, D_obs= 1.42 gm/cm³, D_calc=1.423 g/cm³, 2886 reflections were collected on a CAD‐4 diffractometer. The structure was solved by direct methods and refined to a final reliability index of 4.7%. The galactoside sugar has the chair conformation with C2' and C5' deviating from the mean plane of the other atoms of the sugar. The 4,6‐O‐benzylidene ring also has a chair conformation with the benzoyl group proximal to O6'. The crystal structure is stabilized by O‐H…O hydrogen bonds involving O2' as donor and three C‐H…O hydrogen bond interactions. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal Structure of Diethyl 2‐[2,2,2‐ trifluoro‐1‐(indole‐3‐yl)‐ethyl]‐2‐acetamidomalonate

The title compound (C₁₉H₂₁F₃N₂O₅) has been determined from three dimensional X‐ray diffraction data. The crystals are monoclinic, a = 7.626(4)Å, b = 17.515(4)Å, c = 15.066(3)Å, β = 101.02(3)°, V = 1975(1)ų, Z = 4, D_calc = 1.393g cm^‐3, space group P2₁/c. The structure was solved by direct methods and refined by full‐matrix least‐squares method (R = 0.039).     

Synthesis and structural study of Rb<Subscript>2</Subscript>FeZr(PO<Subscript>4</Subscript>)<Subscript>3</Subscript> phosphate with langbeinite structure

A new orthophosphate of rubidium, iron, and zirconium, crystallizing in the langbeinite structure (cubic system, sp. gr. P2₁3, Z = 4), was synthesized and investigated by X-ray powder diffraction and IR spectroscopy. The structure of the Rb₂FeZr(PO₄)₃ phosphate was refined by the Rietveld method using the neutron powder diffraction data (DN-2 time-of-flight diffractometer; Joint Institute for Nuclear Research, Dubna). This structure is characterized by a mixed framework [FeZr(PO₄)₃] with Rb atoms located in large cavities. Fe³⁺ and Zr⁴⁺ cations are distributed statistically over two independent crystallographic positions.     

Synthesis and structure of new thorium phosphate CaGdTh(PO<Subscript>4</Subscript>)<Subscript>3</Subscript>

Phosphate CaGdTh(PO₄)₃ was prepared by thermal treatment of a mixture of oxides. The final temperature was 1400°C. The phosphate was characterized by powder X-ray diffraction analysis and IR spectroscopy. The crystal structure was studied by the Rietveld method. The compound crystallizes in the monazite structure type (sp. gr. P2₁/n). A comparative analysis of the structures of this phosphate and cerium orthophosphate CePO₄ was carried out.     

Analysis of the crystal structures of 1,3‐di‐tert‐butyl‐2,3‐dihydro‐1H‐1,3,2‐diazasilol‐2‐ylidene and 1,3‐di‐tert‐butyl‐2,2‐dichloro‐1,3‐diaza‐2‐sila‐4‐cyclopentene

The crystal structures of the title compounds, 1,3‐di‐tert‐butyl‐2,3‐dihydro‐1H‐1,3,2‐diazasilol‐2‐ylidene, C₁₀H₂₀N₂Si ( 1 ) and 1,3‐di‐tert‐butyl‐2,2‐dichloro‐1,3‐diaza‐2‐sila‐4‐cyclopentene, C₁₀H₂₀N₂SiCl2 ( 3 ) were solved and are reported. Compound ( 1 ) crystallized in space group P mmn and each molecule has a mirror plane, which bisects the C‐C backbone of the N‐C‐C‐N framework. Compound ( 1 ) was also found to have a 2‐fold twin component. In compound ( 3 ) the space group P 2₁/m results with the mirror plane passing through the N‐C‐C‐N backbone. We compare these structures with the gas phase determination previously reported for ( 1 ) and the incomplete single crystal data for ( 3 ). (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis and X‐ray powder diffraction studies of semiconducting alloys in the system AgCd2‐xZnxGaS4

X‐ray powder technique was used in the investigation of AgCd₂GaS_4–'AgZn₂GaS₄' section to determine the region of AgCd₂GaS₄‐based solubility. It was established that the solid solution forms up to 75 mol.% 'AgZn₂GaS₄'. The refinement of AgCd_0.5Zn_1.5GaS₄ structure was performed. This alloy crystallizes in orthorhombic structure (space group Pmn2₁ ) with unit cell parameters a =0.78772(2), b =0.67221(2), c =0.64019(2) nm, V =0.33899(3) nm³. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The Crystal and Molecular Structure of 11,12‐dibromo‐ 7,8—benzo‐1,5‐di(p—tolylsulphonyl)‐1,5‐diazacyclononan

The crystal structure of the title compound, C₂₅H₂₆Br₂N₂O₄S₂ was determined by single crystal X‐ray diffraction technique. The crystals are monoclinic, space group C 2/c, with a=20.7142(2) Å b=11.7910(2) Å, c= 10.6735(3) Å, β=98.549(2)°, V=2577.94(9) ų, Z=4. The structure was solved by direct methods and refined by least‐squares methods to a final R=0.046 for 1866 observed reflections with I>2sigma(I). The title compound, displays disordered geometry around the C1 atom located almost on twofold axis. The nine‐membered heterocylic ring is close to the half‐chair conformation. The dihedral angle between phenyl rings is 34.2(1)°.