Four powder diffraction patterns taken under different experimental conditions were denoised by a new method, i.e., thresholding of wavelet coefficients. The patterns were transformed by discrete wavelet transform applying Coiflet4 wavelet function. WLS refinements of peaks’ positions, FWHM, and intensity showed that wavelet denoising, in contrast to previously used polynomial smoothing, did not shift the maxima and preserved peak and integrated intensities. This method may therefore represent an useful alternative to polynomial filters or filters based on Fourier transform.

The powder pattern of calcium galactarate tetrahydrate (CaC6H8O8·4H2O) is presented. The compound was found in white wine stored for 4 years. A Rietveld refinement using the atomic coordinates from a single crystal study as starting values was refined with 55 parameters and without preferred orientation to RB=5.97%, RF=4.44%, Rp=10.39%, and Rwp=13.43% for 84 reflections. Crystal data: Mr=320.14, orthorhombic, Pcan, a=7.3359(1) Å, b=11.6296(3) Å, c=15.0978(6) Å, V=1288.05(6) Å3, Z=4, Dx=1.651 g/cm3, λ(CuKα1)=1.54060 Å, μ=46.76 cm−1.

The compounds BaR2O4, where R = La, Nd, Sm, Gd, Eu, Dy, Ho and Er have been prepared from a stoichiometric mixture of BaCO3 and lanthanide oxides, and characterized by X-ray powder diffraction. Standard X-ray patterns of these phases were prepared. In general, BaR2O4 crystallizes in the pervoskite-related CaFe2O4 structure which is orthorhombic with a space group Pnam. The cell parameters of these compounds from R = Er to La range from 10.3729(12) to 10.668(2) Å for a, 12.0699(11) to 12.642(2) Å for b, from 3.4356(4) to 3.7037(10) Å for c, and from 450.14(5) Å3 to 499.51 Å3 for V respectively. A monotonic, linear relationship is obtained when V is plotted against the cube of the ionic radius of R. When R = Tm, Lu and Yb, the BaO·R2O3 composition produced the mixture Ba3R4O9 and the unreacted lanthanide oxide. Under the present experimental conditions, the compound BaRO3 was the predominant component when R = Ce, Pr, and Tb.

An improved method of alignment of a Philips diffractometer equipped with a theta-compensating slit is described. The method employs a special fluorescent screen which is flat to better than 10 microns. The procedure results in accurate alignment of the theta-compensating slit at low angles and assures reliable intensity data down to one degree two theta or less.

X-ray powder diffraction is one of the most sensitive methods for the analysis of crystalline forms of silica. In addition to detection and quantification, it can determine the specific crystalline species in the sample. The principal limitations of the method depend on the effective volume of the sample in the X-ray beam and the number of crystallites in the proper orientation to diffract. Detection limits are usually reported as 2 μg in thin-film filter mounts and 0.1% in bulk samples that are free of interference from associated minerals. Filter methods are most often used for air quality monitoring and several standardized procedures have been certified. Standard procedures for bulk samples are difficult to certify because of the variability of the matrices and their potential interferences. All of the methods of quantification require calibration with known samples of quartz or cristobalite. Certification of standard samples involves characterization of the particle and crystallite size and size distribution and amorphous content as well as determining the X-ray diffraction response. Although quartz is readily available and cristobalite is easy to synthesize, preparation of quantities of sufficient uniformity and stability is a limiting factor in certifying such samples for reasonable costs. Conventional diffraction equipment can be used for crystalline silica analysis at the present detection limits required by safety standards. Relatively simple modifications of the diffractometer will increase its sensitivity to small amounts of silica and improve the lower limits of quantification.

Single crystals of Cs3A[B2(SCN)7] with A = Sr, Ba and B = Ag, Cu have been synthesized from aqueous solutions by the evaporation method. The complex thiocyanates are isostructural and crystallize in the tetragonal system with space group .

Complete crystal data and optical data for the four compounds are reported. An X-ray powder diffraction pattern for Cs3Sr[Cu2(SCN)7] is given.

A new and improved sample holder for use with powder X-ray diffractometry has been developed. This holder is made from a semiconductor grade silicon single crystal cut perpendicular to the [911] axis, i.e., Si (911). This crystal meets most of the basic requirements of an ideal zero background plate, with practically no interference lines. The pattern obtained, by using this crystal as background plate, is very clean, and even very low-intensity Bragg reflections of samples can be detected easily.

Precise X-ray powder diffraction patterns of hydrated and anhydrous thallium pentaborates have been collected on a D5000 diffractometer with a primary monochromated beam (λ Cu Kα1=1.5406 Å). Refinement of indexed reflections led to the following unit cell parameters: a=11.279(1)Å, b=7.1507(6)Å, c=13.953(1)Å, β=94.164(7)° in the P21/c space group with Z=4, Dx=2.713 gcm−3, Dm=2.6 gcm−3 for Tl[B5O6(OH)4]·2H2O and a=7.5698(5)Å, b=11.9509(6)Å, c=14.759(1)Å in the Pbca space group with Z=8, Dx=3.844 gcm−3, Dm=3.6 gcm−3 for TlB5O8. Very good Smith and Snyder figures of merit have been obtained: F30=139.7 (0.0043, 50) for Tl[B5O6(OH)4]·2H2O and F30=139.3 (0.0054, 40) for TlB5O8.

Charles Barrett's work in phase transformation at the atomic level helped redefine the underpinnings of the science and practice of metallurgy. His work in low temperature physical chemistry has extended its range. And, perhaps more than anyone else, as a teacher and author, he has helped introduce the technique of X-ray diffraction to the present generations of practicing metallurgists.

The relevance of his contributions is demonstrated by the continuing utility of his widely translated metallurgical text, Structure of Metals, which, when it first appeared, made the understanding of metallurgy at the atomic level accessible to a wide audience. Today this book has become a compendium of first principles.

The crystal structure of cobalt(II) acetate tetrahydrate, Co(C2H3O2)·4H2O, has been refined using single-crystal, laboratory powder, and synchrotron powder diffraction data, both individually and in various combinations. The compound crystallizes in the monoclinic space group P21/c, with a=4.80688(3), b=11.92012(7), c=8.45992(5) Å, β=94.3416(4)° at 27 °C, and Z=2. The crystal structure consists of discrete centrosymmetric trans-Co(C2H3O2)(H2O)4 complexes, linked by a three-dimensional network of hydrogen bonds. Each complex participates in 14 hydrogen bonds, 12 intermolecular, and 2 intramolecular. Compared to the single-crystal refinement, refinement of laboratory powder data yielded an average difference in bond distances of 0.02 Å, in bond angles of 3°, and in root mean square atomic displacements of 0.07 Å. The standard uncertainties of the bond distances were 0.01 Å, compared to the 0.001–0.002 Å in the single-crystal refinement. Refinement of the synchrotron powder data yielded improved accuracy and precision. It proved impossible to locate or refine hydrogen positions using a single-powder dataset, but the hydrogens could be refined using rigid groups in a joint refinement of the two powder datasets. Even from powder refinements, it is possible to obtain suitable accuracy and precision to distinguish C–O and C=O bonds, and to examine details of chemical bonding.

X-ray powder diffraction analysis of the complex of Benzo-15-Crown-5 (B-15-Crown-5) with NaClO4 displays a monoclinic crystal system with refined unit cell parameters of a = 8.829(3)Å, b = 8.327(3)Å, c = 24.21(2)Å, ß = 99.18(1)Å, V = 1757.1(1)Å3, Z = 4, and Dx = 1.48 g/cm3. The space group, P21/c, and the unit cell dimensions, determined by a single crystal diffraction analysis, agree well with those of the powder analysis. X-ray powder diffraction analysis of the complex of B-15-Crown-5 with KI displays a tetragonal crystal system with refined unit cell dimensions of a = b = 17.869(3)Å, c = 9.761(3)Å, V = 3116.7(1)Å3, Z = 4, and Dx = 1.50 g/cm3. The space group, P4/n, and the unit cell dimensions, determined by a single crystal diffraction analysis, agree well with those of die powder diffraction analysis. The powder and single crystal analyses of the two complexes indicate that in the solid phase, B-15-Crown-5 forms a 1:1 complex with Na+ and a 2:1 complex with K+. The variation in the complexation mode of B-15-Crown-5 with different cations, partially explains the lack of selectivity of this crown ether towards Na+, while from considerations of the cavity size alone this crown ether was expected to be considerably selective towards this cation.

Quantitative phase analysis of n-phase mixtures can be performed if at least n samples composed of no more than n identical phases are available. The fact that there is no need for pure phases (analytical standards) constitutes the main advantage of the method presented here. However, substitution for the pure phases by an unknown mixture of these phases decreases the diversity of the sample set and also the precision of the analysis. The crucial step in a standardless method is the creation of an initial sample set. A simple test is developed to estimate the suitability of the sample set for analysis and to evaluate the analysis error. Application of this test to 13 four-phase mixtures has confirmed its high quality.