The International Centre for Diffraction Data has a colorful history, starting as a small task group of involved and interested scientists and progressing through a number of evolutionary steps that were required to deliver scientific products and services globally. The results of these efforts can be found in numerous scientific publications that focus on basic physics, method development, and analyses of the material identification of solid-state materials. This article examines the evolution of the organization through its members and employees.

Phase transitions were found with use of an in situX-ray anvil-type of apparatus with a boron annulus at pressures up to 12 GPa. The disordering of vacancies in the In sub-structure, or α→βtransition, was found in In2Te3at p > 1.9 GPa. The next transformation from the β-form into the Bi2Te3type of structure was observed in both sesquitellurides at 2.0 GPa and 5.0 GPa for In2TGe3and Ga2Te3respectively. The In2Te3metastable phase of the Bi2Te3resulted from heating up to 200° C at p > 4.0 GPa, and it remained in a normal condition on release of the pressure. The X-ray powder diffraction data of pressure-induced phases, volume changes and bulk modulus of both sesquitellurides are given. The compressibility anisotropy of the layer pressure-induced phase was observed. The mechanism of the crystal structure transformation from the face-centered cubic structure into the Bi2Te3type is proposed to be due to the displacement of atoms from the space diagonal of the cube [111] into [112]-cubic direction and the rhombohedral distortion of the angle between these directions.

The use of high-speed detectors made X-ray diffraction (XRD) become an important tool for process control in mining and metal industries. Decreasing ore qualities and increasing prices for raw materials require a better control of processed ore and a more efficient use of energy. Traditionally quality control of iron ore sinter has relied on time-consuming wet chemistry. The mineralogical composition that defines the physical properties such as hardness or reducibility is not monitored. XRD analysis in combination with Rietveld quantification and statistical data evaluation using partial least-squares regression (PLSR) has been successfully established to determine the mineralogical composition and the Fe2+ content of iron ore sinter within an analysis time of less than 10 min per sample. A total of 35 iron ore sinter samples were measured and evaluated using PLSR and the Rietveld method. The results were compared with wet chemistry data. PLSR results show accuracy for the Fe2+ content of ±0.14%. No pure phases, crystal structures, or complex modeling of peak shapes are required. The Rietveld method was used to quantify the total phase composition of the samples. The Fe2+ content could be calculated from all phases present. Both methods take the full XRD pattern into account and can be simultaneously applied on the same measurement. PLSR was found to be the more robust method if only Fe2+ results are required. The Rietveld method helps predict other parameters such as the compressional strength of the sinter by monitoring all existing phases (e.g., larnite, C2S, or silico-ferrite of calcium and aluminum phases).

Trigonal CdSb2O6, prepared as a very crystalline powder by solid state reaction of CdO and Sb2O3, is isostructural with PbSb2O6 Space Group (S.G.) P31m (162), with a = 5.2399(2), c = 4.8045(4) Å, Z = 1 and Dc = 6.57 Mg.m−3. For the refinement of structural parameters from X-ray powder diffraction data two different methods have been employed and compared, both leading to very similar results. The refinements converged to RI = 0.025 using 35 intensities in the incremental optimization technique and to RF = 0.038, RW = 0.033 from 161 reflections in the least-squares refinement.

The crystal structure of Sb(C2O4)OH has been solved by charge flipping in combination with difference Fourier techniques using laboratory X-ray powder data exhibiting significant preferred orientation and refined by the Rietveld method. The compound crystallizes in Pnma with a=5.827 13(3), b=11.294 48 (10), c=6.313 77(3) Å, V=415.537(5) Å3, and Z=4. The crystal structure contains pentagonal pyramidal Sb3+ cations, which are bridged by hydroxyl groups to form zigzag chains along the a axis. Each oxalate anion chelates to two Sb in approximately the ab plane, linking the chains into a three-dimensional framework. The H of the hydroxyl group is probably disordered in order to form stronger more-linear hydrogen bonds. The highest energy occupied molecular orbitals are the Sb3+ lone pairs. The structure is chemically reasonable compared to other antimony oxalates and to Bi(C2O4)OH.

We know a lot about normal values of bond distances, bond angles, torsion angles, and other molecular parameters. This knowledge can be incorporated into the structure solution process and into Rietveld refinement through the use of restraints and rigid bodies. An important measure of the quality of the refined model is the chemical reasonableness of molecular geometry. Refinement of the structures of calcium tartrate tetrahydrate and guaifenesin is used to illustrate the importance of chemical reasonableness in determining the quality of a Rietveld refinement.

The crystal structures of Sr2MgWO6 and Ba2SrWO6 compounds, studied by powder X-ray diffraction, were found to be distorted perovskites with a complete NaCl type ordering between Mg2+/W6+ and Sr2+/W6+ ions, respectively. The unit cells are characterized by the tetragonal (space group I4/m; a0a0a−) symmetry, with the parameters a=5.5849(10) Å and c=7.9455(10) Å, for Sr2MgWO6 and triclinic (space group F-1; a−b−b−) symmetry, with the parameters a=8.5409(10) Å, b=c=8.5860(10) Å, α=89.35(1)° and β=γ=90.31(1)°, for Ba2SrWO6. © 2004 International Centre for Diffraction Data.

In the investigation of MgO–Y2O3–B2O3 system, six three-phase regions, five binary compounds, and one ternary compound MgYB5O10 were confirmed in the subsolidus phase relations. Single-phase powder sample of MgYB5O10 was successfully prepared through solution synthesis method. By using the Rietveld method from the step-scanning X-ray powder diffraction data, the crystal structure of MgYB5O10 was determined. It crystallizes in the monoclinic system with the space group P121/c1 and lattice parameters a = 8.5113(2) Å, b = 7.5892(2) Å, c = 12.2460(3) Å, β = 130.200(1)°, and Z = 4. The infrared spectrum of MgYB5O10 at room temperature demonstrates the existence of BO3 and BO4 groups. The UV–visible spectrum shows a wide absorption band within the range of 190–400 nm, while the absorption in the visible region is negligible. According to the electronic structure derived by first-principles calculations, MgYB5O10 is an insulator with a wide indirect energy band gap of about 5.95 eV. Layered structural characteristics, existence of one-dimensional YnO8n+2 chains, and the large band gap should be the immanent reason why MgYB5O10-based materials have exhibited outstanding performances in the luminescence field.

The crystal structure of the natural zeolite garronite from Goble, Oregon has been refined using high resolution synchrotron X-ray powder diffraction data. Garronite has the same tetrahedral aluminosilicate framework as gismondine [GIS], and earlier structural models indicated a strong tetragonal pseudosymmetry. Proposed models in the literature were based on the I4¯m2 and I41/a space groups, on account of symmetry lowering from the topological I41/amd space due to partial cation/water molecule order in the zeolitic cavities. Test structure analysis has been performed in all possible space subgroups including monoclinic space groups, and the refinement has been successfully carried out in space group I2/a (C2/c). The resulting monoclinic structure model is to be preferred over the tetragonal ones on the basis of: (1) lower agreement indices of the refinement; (2) a chemically sound framework geometry; and (3) a more satisfactory interpretation of the Ca atoms coordination in the extraframework cages.

It is well known that all of the six independent components of the strain tensor can be calculated if the linear strains in six appropriate directions are known (e.g.). That calculation is to solve a system of linear equations, whose coefficients are defined by the orientations of the measured planes. The strains are determined by lattice plane distance measurements using X-rays.

The linear equation system can only be solved if the matrix of coefficients has rank. Whether this condition is met or not can be decided without calculating a determinant just from geometric relationships among the planes to be measured. A demand beyond that necessary condition is to make the matrix of coefficients so that the accuracy of the calculated strain tensor is best. From error calculation we know that there exist distinct ratios between the inevitable measurement errors and the errors of the calculated strain components. These ratios depend strongly on the geometric relationship among the lattice planes. It is the purpose of this paper to show how lattice planes should be chosen in order to get these ratios as small as possible i.e. to get a maximum of accuracy at a given number of measurements, or a minimum of experimental effort if a distinct limit of error is to be reached.

SIROQUANT is a suite of personal ccmputer programs which runs on an IBM-compatible 386 or 486 personal computer, and gives phase quantification of mineral samples hy Rietveld refinement using the full XRD profile. Eight phases can be quantified in a mineral with the 640 K RAM version and 11 in the EM version.

New features have been added since the original description was written (J.C. Taylor, Powder Diffraction, 6, 2, 1991) including calculations of amorphous percentages using spiked samples, particle size calculations, use of “measured” as well as calculated patterns as standards, pre-programmed refinement “Stages” with different variables in each stage, and improved menus.

Some advanced applications of the system using these new features are described.

A review of the methods of characterization of materials using X-rays incident at grazing angles is presented. The rationale of all such methods is the need to obtain information from near-surface regions. The methods include grazing incidence diffraction, reflectivity, diffuse scatter and fluorescence. The experimental techniques are outlined, and the information obtainable and the methods of interpretation are discussed.

The broadening of powder pattern peaks has been studied by three methods—Fourier analysis, integral breadth measurements, and variance of the line profiles. The results obtained from the variances are compared with those obtained from the integral breadths and Fourier coefficients.

Tungsten filings were prepared at room temperature and their powder pattern peaks were recorded with a Norelco diffractometer using filtered Cu Kα radiation. The variances, integral breadths, and Fourier coefficients were calculated with the IBM 7094 computer. The results indicate that the variance is very sensitive to the range of integration s2 − s1 = (2θ2 − 2θ1) cos θ0/λ. An error of ± 10% in this range due to the difficulty in choosing the correct background changes the values of the variance significantly and the integral breadth to a lesser extent. However, the same error does not affect the values of the Fourier coefficients.

Comparing the particle sizes and strains obtained by the three methods, it was found that the strains agreed remarkably well. The particle size calculated from the variance was smaller (DeW = 150Å) than that evaluated from the initial slope of the Fourier coefficients (De – 210Å) and from the integral breadths 2De ≃ D1 = 430Å.

The structure of the Ba5R8Zn4O21 series (R=lanthanides) was investigated using X-ray Rietveld refinements. The compounds were successfully prepared for R=Eu, Gd, Dy, Ho, Er, Tm, and Yb. Ba5R8Zn4O21 crystallizes in the tetragonal space group I4/m; for R=Yb to Eu, a ranges from 13.635 02(5) to 13.960 62(9) Å, c from 5.658 46(3) to 5.784 83(5) Å, and V from 1051.987(8) to 1127.459(14) Å3. The Zn2+ ions adopt a fivefold distorted square pyramidal coordination. The seven-coordinate R3+ reside in monocapped trigonal prisms. These prisms share edges, and form layers stacked along the c axis. There are two types of BaO polyhedra: bicapped square prisms (BaO10), and irregular BaO10 polyhedra. For larger R, Ba5R8Zn4O21 was not stable, and tetragonal BaR2ZnO5(La, Nd) and orthorhombic BaR2ZnO5(Sm) phases were observed instead.

Twenty seven new rare earth (Ln) compounds CuLn2 Ge2O8, CuLn2Ge4O12 and CuLn2Si4O12 have been synthesized. The powder diagrams were indexed and solid solutions of silicates and germanates were investigated. Structural variations with temperature, lanthanide contraction and Ge/Si substitution are described. Indications for second order phase transitions were found.

Crystallographic structures of two new orthophosphates Ca0.50SbFe(PO4)3 and CaSb0.50Fe1.50(PO4)3 obtained by conventional solid state reaction techniques at 900 °C, were determined at room temperature from X-ray powder diffraction using Rietveld analysis. The two compounds belong to the Nasicon structural family. The space group is R3 for Ca0.50SbFe(PO4)3 and R3c for CaSb0.50Fe1.50(PO4)3. Hexagonal cell parameters for Ca0.50SbFe(PO4)3 and CaSb0.50Fe1.50(PO4)3 are: a=8.257(1) Å, c=22.276(2) Å, and a=8.514(1) Å, c=21.871(2) Å, respectively. Ca2+ and vacancies in {[Ca0.50]3a[◻0.50]3b}M1SbFe(PO4)3 are ordered within the two positions, 3a and 3b, of M1 sites. Structure refinements show also a quasi-ordered distribution of Sb5+ and Fe3+ ions within the Nasicon framework. Thus, in {[Ca0.50]3a[◻0.50]3b}M1SbFe(PO4)3, each Ca(3a)O6 octahedron shares two faces with two Fe3+O6 octahedra and each vacancy (◻(3b)O6) site is located between two Sb5+O6 octahedra. In [Ca]M1Sb0.50Fe1.50(PO4)3 compound (R3c space group), all M1 sites are occupied by Ca2+ and the Sb5+ and Fe3+ ions are randomly distributed within the Nasicon framework.

The procedure of whole-powder-pattern fitting without reference to a structural model has been applied to the determination of direction-dependent crystallite size and strain. The fitting function used is defined as the sum of (1) background intensity and (2) contributions from individual reflections given as the convolution of the observed instrumental function with the true data function in analytical form. Crystallite size and strain parameters are adjustable, together with unit-cell parameters and the integrated intensities of all reflections, during the whole-powder-pattern fitting. The procedure requires neither structural parameters nor intensity correction for preferred orientation in calculating profile intensity. The two models are incorporated for line broadening, one for isotropic size and strain effects and the other for the anisotropic size effect of cylindrical shape. The procedure has been tested for these two models using the observed data of 4 mole % Y2O3-doped tetragonal ZrO2 and hydroxyapatite, Ca5(PO4)3OH, respectively, and been shown to be effective for determining crystallite size and strain from the powder pattern with a relatively high peak density.

Tooth enamel, the outermost layer of human teeth, is a complex, hierarchically structured biocomposite. The details of this structure are important in multiple human health contexts, from understanding the progression of dental caries (tooth decay) to understanding the process of amelogenesis and related developmental defects. Enamel is composed primarily of long, nanoscale crystallites of hydroxyapatite that are bundled by the thousands to form micron-scale rods. Studies with transmission electron microscopy show the relationships between small groups of crystallites and X-ray diffraction characterize averages over many rods, but the direct measurement of variations in local crystallographic structure across and between enamel rods has been missing. Here, we describe a synchrotron X-ray-based experimental approach and a novel analysis method developed to address this gap in knowledge. A ~500-nm-wide beam of monochromatic X-rays in conjunction with a sample section only 1 μm in thickness enables 2D diffraction patterns to be collected from small well-separated volumes within the enamel microstructure but still probes enough crystallites (~300 per pattern) to extract population-level statistics on crystallographic features like lattice parameter, crystallite size, and orientation distributions. Furthermore, the development of a quantitative metric to characterize relative order and disorder based on the azimuthal autocorrelation of diffracted intensity enables these crystallographic measurements to be correlated with their location within the enamel microstructure (e.g., between rod and interrod regions). These methods represent a step forward in the characterization of human enamel and will elucidate the variation of the crystallographic structure across and between enamel rods for the first time.

Three powder mixtures, each composed of four or more phases, were submitted for phase identification by x-ray diffraction. Laboratory technicians supplied tables of “d” values and of relative intensities as obtained separately and independently by use of the diffractometer, the Debye camera and the Guinier camera. These tables of diffraction data were “solved” by utilization of the Joint Committee search manuals and reference to the Joint Committee Powder Diffraction File (P.D.F.). The same tables of data were then submitted to the 2dTS:Diffraction Data Tele∼Search for a computer printout of results. Experimental data are also presented which provide a quantitative comparison of the accuracy of measurement of “d” values and of the resolution of Debye cameras vs Guinier cameras, since this information is necessary for efficient search procedures whether by manual or computer methods.

The incorporation of carbonate in the apatite causes a decrease in crystallite size as demonstrated in precipitated apatites prepared at 37°C. Carbonate disturbs the crystallization of the growing apatite crystallites to such an extent that materials with more than 15 wt% CO3 gives an ‘amorphous’ x-ray diffraction pattern. The incorporation of carbonate in precipitates prepared at 100°C. causes a shortening of the a-axis and a lengthening of the c-axis which is proportional to the carbonate content, supporting the concept that in these apatites, CO3 substitutes for PO4 (11). X-ray diffraction linebroadening studies of CO3-apatites precipitated at 100°C and electron micrographs show that the size and shape of the crystallites change from long needles to smaller rods to tiny spheroids, depending upon the amount of CO3. Carbonate causes the bonding in the apatite to become weaker and more isotropic, which results in the small spheroidal crystals.

This paper reports the effect of carbonate on lattice parameters and morphology of carbonate-apatites which have been prepared by the conversion of rnonetite, CaHPO4 in hot carbonate solutions. The structural effects of CO3 on the apatite is further reflected by the modification of the vibrations of the PO4 groups in the infrared absorption spectra. The morphology of ‘amorphous’ CO3- containing apatitic precipitates and that of CO3∼apatite with high CO3 content (prepared at 100°C) is similar, i.e., spheroidal in shape, but greatly differing in crystallite size.