In the absence of single crystals, silver(I) 3,5-dimethylpyrazolate, [Ag(dmpz)]3, has been structurally characterized by ab initio X-ray powder diffraction, using conventional laboratory data. Its crystals are triclinic, P1¯, with a=8.0876(10), b=11.1204(13), c=11.6136(16) Å, α=68.293(6), β=78.350(7), and γ=81.243(6)°. The structure has been solved by Patterson, difference Fourier, and geometrical modeling, and ultimately refined by the Rietveld method down to Rp=0.068, Rwp=0.085, and RF=0.055, for 4300 observations in the 17<2θ<103° range. Each molecule consists of a cyclic, trimeric assembly of Ag(dmpz) fragments, with the dmpz ligand bridging, in the exo-bidentate mode, nonbonded Ag…Ag edges.

The structure of Ba7Cl2F12 has been determined ab initio from conventional X-ray powder diffraction data by the “heavy atom” method. The cell is hexagonal (space group P6¯, Z=1), with a=10.6373(2) Å and c=4.1724(2) Å. Refinement of 38 parameters by the Rietveld method, using 278 reflections, leads to cRwp=0.173, cRp=0.135, and RB=0.054. The structure has common characteristics with that of the other BaF2-rich fluorochloride, Ba12Cl5F19. In both phases Ba2+ ions lie in tricapped trigonal prisms formed by nine halide ions, and Cl− ions occupy the center of trigonal prisms of Ba2+ ions. F− ions are located in cationic tetrahedra or square pyramids.

Samples of the mineral ferroan clinozoisite from three localities of Greece (Paranesti-Drama, Xanthi, and Petritsi-Serres), with chemical formula Ca2Al3−xFexSi3O13H (x=0.55, 0.58, and 0.46, respectively), were measured by X-ray powder diffraction, using CoKa radiation. The PDF and bibliographic information were used in order to identify additional phases in the samples. Refinement combined with PDF resulted in the following: ferroan clinozoisite (100%) for the first sample, ferroan clinozoisite (97%) and malladrite (3%) for the second one, and ferroan clinozoisite (75%), clinopyroxene (20%), and malladrite (5%) for the third one. The crystal structure refinement was performed by the “Powder profile analysis (Rietveld)”. P21/m space group was chosen for the ferroan clinozoisite phases, with unit cell constants a=8.8919(5) Å, b=5.6260(3) Å, c=10.1570(6) Å, β=115.418(3)° (Paranesti), a=8.8944(7) Å, b=5.6394(4) Å, c=10.1626(8) Å, β=115.400(5)° (Xanthi) a=8.8965(8) Å, b=5.6372(4) Å, c=10.1595(9) Å, β=115.411(6)° (Petritsi) almost similar for the three samples, while the final R-p factors were 0.069, 0.064, and 0.063, respectively.

As part of a study by high-resolution X-ray diffraction of chrome ores from the Great Dyke, Zimbabwe, powder data are reported for a well-crystallized ferroan magnesiochromite spinel, in which some Cr had been replaced by Al. Data were obtained by using CuKα1 radiation, with an incident beam focusing monochromator to eliminate the Kα2 component. The cell parameter is a0=8.3123(2) Å, the figures of merit are M17=383 and F17=182 (0.0055, 17) and the calculated density is 4.50(5) Mgm−3. A small amount of sample broadening was observed and this was attributed to a mean crystallite size of 259(1) nm. © 1997 International Center for Diffraction Data.

Powder X-ray diffraction data for Ba12Cl5F19 are reported. The cell is hexagonal (space group P6¯2m, Z=1), with a=14.0856(3) Å and c=4.2733(2) Å.

An experimental investigation has been carried out to determine the extent to which axial divergence in a conventional powder diffractometer influences the measurement of peak profile parameters. A Siemens D5000 θ–2θ diffractometer was used for this study along with the LaB6 line profile standard SRM 660. Eight unique levels of axial divergence were investigated either by removing one or more of the Soller slits, or by introducing different combinations of Soller slits in the incident and diffracted beams. The measure of axial divergence used throughout is based on the maximum axial divergences of the incident and diffracted beams, Ψi and Ψd. Axial divergence produces a small and almost constant shift δ2θp in the peak angle which in a typical diffractometer would amount to a zero offset 2θ≈0.005°. The integrated intensity of a profile increases almost linearly with the product Ψi*Ψd. The increase in breadth in profiles in the angular region 2θ<120° arises mainly from the change in asymmetry DH=Hlo−Hhi in which one side of the profile broadens (i.e., either the high angle or low angle side) without any significant broadening of the other side. Moreover, the asymmetry DH is linearly dependent on 2θ for a fixed level of axial divergence, and linearly dependent on the total axial divergence Ψi+Ψd at fixed 2θ.

Three new mixed oxides having the nasicon structure and containing arsenic(V) as tetrahedral ion were prepared and X-ray analyzed. The stoichiometry of the three phases can be expressed by the comprehensive notation MeZr2As(3−x)PxO12 where Me stands for Na+ or K+, x equals to 0 and 1.5 when Me=Na, while x equals to 1.5 when Me=K. For two other compositions of the above series, the powder patterns were calculated on the basis of the structural data from single crystal determinations, thus permitting us to complete the characterization of the solids, with nasicon framework, deriving from MeZr2P3O12 (Me=Na+, K+) by partial (50%) or complete (100%) substitution of As for P.

Key words: nasicon, ionic conductors, phosphates, arsenates

A nonlinear optical material, 1-benzoyl-3-(4-benzyl)thiourea (C15H14N2OS), has been characterized by X-ray powder diffraction. Experimental values of 2θ corrected for systematic errors, relative peak intensities, values of d, and the Miller indices of 82 observed reflections with 2θ up to 80° are reported. The powder diffraction data have been evaluated, and the figures-of-merit are reported. The least-squares refined unit cell parameters are a=22.0243(6)Å, b=10.9795(7)Å, c=13.0322(8)Å, β=116.88(2)°, V=2810.8(9)Å3, Z=8, Dx=1.278 g/cm3, space group Pn.

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.

The structure of Co2Al5 (hP28, P63/mmc) was refined by means of Rietveld method. The shortest Co–Al distance amounts 2.338 Å. Co2Al5 shows a homogeneity range between Co29Al71 and Co27.5Al72.5 at 1125 K. The concentration dependence of lattice parameters was also measured. The axial ratio c/a increases with increasing mole fraction of aluminum.

Cu2Th4(MoO4)9 is cubic: a=14.4856(1) Å, space group I4¯3d, Z=4. Its crystal structure was recently determined using a single crystal. The results of chemical study allow one to reject the existence of Li4Th7(MO4)16 and La(MO4)(ReO4) compounds with M=Mo, W, reported as isostructural with Cu2Th4(MoO4)9. Precise X-ray powder patterns are established for Cu2Th4(MoO4)9 and isotypic compounds Li2Th4(MoO4)9, Li2Th4(WO4)9, and La4(MoO4)3(ReO4)6.

Chapmanite, Sb(OH)Fe2(SiO4)2 is a rare mineral that generally occurs as yellow coatings on rocks from antimony mines. The very small dimensions of the crystals prevented X-ray, single-crystal study of the mineral whose structure was derived through high voltage electron diffraction (Zhukhlistov and Zvyagin, 1977). The present study confirm the correctness of the structure determined by those authors and also shows the effectiveness of the Rietveld method in the case of highly diluted phases. The structure of chapmanite is similar to that of kaolinite with two major differences: (a) the dioctahedral sheet of chapmanite contains Fe3+ instead of Al3+; (b) chapmanite has cations grasped to the octahedral sheet, on the opposite side with respect to the tetrahedral sheet.

The X-ray powder diffraction patterns for three bulk Zn1−xMgxSe crystals are reported. The data were obtained with the help of an automated Bragg–Brentano diffractometer using Ni-filtered Cu Kα radiation. One of the samples is of the sphalerite structure type, and it has the magnesium content slightly below the sphalerite–wurtzite phase transition. The two remaining ones are of the wurtzite type with low and high magnesium content. The lattice constant for the sphalerite Zn0.86Mg0.14Se is a0=5.7011(1) Å. For the wurtzite alloys the lattice constants are a0=4.0540(1) Å, c0=6.6270(2) Å (for Zn0.72Mg0.28Se), a0=4.1195(1) Å, c0=6.6941(2) Å (for Zn0.37Mg0.63Se).

The crystal structure of the rare earth (RE) compound CeFeGe3 has been studied by X-ray powder diffraction and refined by the Rietveld profile fitting method. The compound has the tetragonal BaNiSn3-type structure, space group I4mm (No. 107) a=4.3294(1) Å, c=9.9444(3) Å, V=186.39 Å3, Z=2, and Dx=7.372 g·cm−3. The figure of merit FN for the powder data is F30=184.3(0.0037,44). The structure refinement was performed with 106 reflections and led to Rp=13.2% and Rwp=18.2%. Powder data are given.

Four compounds in the hexafluoroniobates IV series MNbF6 (M=Ca, Mg, Cd, Zn) have been synthesized by solid-state reactions. CaNbF6, MgNbF6, and the “high temperature” form of CdNbF6 are isostructural with f.c. cubic NaSbF6 (space group Fm3m). ZnNbF6 and the room temperature form of CdNbF6 are isostructural with rhombohedral LiSbF6 (space group R3¯). Syntheses and powder diffraction data are reported.

Sm2Bi2Ti3O12 was synthesized by solid state reaction from Sm2O3, Bi2O3, and TiO2 in molar relation 1:1:3. Title compound is isostructural with Bi4Ti3O12. Products of the reaction were analyzed by X-ray diffraction methods. The crystal structure was refinement by the Rietveld Method. Cell parameters are: a=5.368(2), b=5.369(2), and c=32.71(2) Å, space group Fmmm. The final R value was 9.96% (Rw=13.43%).© 1998 International Center for Diffraction Data.

Two structurally related compounds, Tl3Li(MoO4)2 and Tl3Li(WO4)2, have been synthesized by solid state reaction. Space group (P63mc) and unit-cell parameters [a(Å)=6.00392(3); c(Å)=15.8203(1) and a(Å)=6.03484(3); c(Å)=15.81759(9), respectively, for Tl3Li(MoO4)2 and Tl3Li(WO4)2] were determined. Powder diffraction data for each phase are reported.

Mass attenuation coefficient corrections, for Rietveld phase analysis with an external compositional calibration standard, may be made using Compton scattering intensities measured by X-ray fluorescence spectrometry. The method is mainly useful for Rietveld phase analysis when mixing an internal standard is impossible or undesirable. The validity of the method has been demonstrated using a suite of alumina-zirconia powders of known composition. Also presented are results for a typical application—determination of phase composition depth profiles defining the graded compositional character of an aluminium titanate/zirconia-alumina ceramic composite.