A Monte Carlo code for indexing powder diffraction patterns is presented. Cell parameters are generated randomly and tested against an idealized powder profile generated from the extracted d’s and I’s. Limits with this program in solving problems associated with zeropoint errors and impurity lines are examined. Most problems (V<2000 Å3, cell parameters <20 Å) are solved in less than 1–15 min if the symmetry is as low as monoclinic (with a >2 GHz processor); more time is needed for triclinic cases. Attempts are shown to be successful for the indexation of two-phase samples in simple cases (combining orthorhombic or higher symmetries). © 2004 International Centre for Diffraction Data.

Key words: powder diffraction, indexing, Monte Carlo

Calcium sodium iminodisulphonate trihydrate was first described by Divers and Haga [J. Chem. Soc. 943–968, (1892)]. It has recently been found as one of several crystalline products resulting from the removal of sulphur dioxide from flue gas. It has not so far been included in the ICCD powder diffraction file.

Powder X-ray diffraction data for a new palladium(II) amino acid complex, of composition PdC12H20N2O4S2, are presented in this paper. Orthorhombic cell parameters are: a=10.740 Å, b=19.999 Å, and c=5.2470 Å. © 2004 International Centre for Diffraction Data.

We have used synchrotron X-ray diffraction experiments to measure the strain field introduced by a hydride blister grown on a section of a pressure tube from a CANDU nuclear reactor. After charging the tube section with a homogeneous hydrogen concentration of 300 wt ppm, the blister was produced by creating a small cold spot on its surface (∼200 °C), while the bulk was kept at a temperature of 338 °C over a period of 1008 h. The blister studied here is ellipsoidal in shape, with its long axis along the tube axial direction. The experiments were performed on the wiggler beam line ID15 at the European Synchrotron Radiation Facility (ESRF) using a polychromatic beam of high-energy X-rays (60 to 300 keV). Unlike conventional X-ray diffraction, in this mode the scattering angle is fixed and the diffracted beam is discriminated on the basis of the photon energy. The results show that the blister is composed by two crystallographic phases (δ-ZrH and α-Zr), with volume fractions varying with position. The maximum stresses appear at the blister-matrix interfaces. Near the tube outer surface, we found large compressive stresses of (−450±90) MPa along the blister long axis, and tensile stresses (+320±90) MPa along the tube hoop direction. The main uncertainty in these stresses results from the uncertainty in the elastic constants of the hydride phase. Large strains and broad peaks were observed for this phase, which were explained by a rather low Young’s modulus (35 GPa) for the hydride. The results are compared with finite element simulations found in the literature.

Preparing dry specimens from liquid samples for XRF analysis avoids introducing caustic or hazardous liquids into the instrument. Several modifications were made to a dried residue specimen preparation method for quantifying gallium in plutonium metal in order to improve the method accuracy and precision. Ion exchange chromatography was utilized to remove the plutonium prior to casting the dried residue specimens. This, coupled with several other changes, improved the method relative error from ∼5% to less than 1%. These results are sufficient for routine sample analysis and are almost comparable to results from the established process using liquid specimens. However, the analysis of radioactive liquid specimens is unnecessary for quantifying the plutonium gallium content using this dried residue approach

The Lorenz-polarization (LP) factor, which is used for X-ray intensity calculations from polycrystalline materials, contains a term that describes the fraction of diffracting grains in the irradiated sample volume. We present extensions of this term and a series of experiments that tests its applicability. The implications of the analysis on microbeam diffraction are also discussed.

In this paper we describe the capabilities for texture measurements of the new neutron time-of-flight diffractometer HIPPO at the Los Alamos Neutron Science Center. The orientation distribution function (ODF) is extracted from multiple neutron time-of-flight histograms using the full-pattern analysis first described by Rietveld. Both, the well-established description of the ODF using spherical harmonics functions and the WIMV method, more recently introduced for the analysis of time-of-flight data, are available to routinely derive the ODF from HIPPO data. At ambient conditions, total count time of less than one hour is ample to collect sufficient data for texture analysis in most cases. The large sample throughput for texture measurements at ambient conditions possible with HIPPO requires a robust and reliable, semi-automated data analysis. HIPPO’s unique capabilities to measure large quantities of ambient condition samples and to measure texture at temperature and uni-axial stress are described. Examples for all types of texture measurements are given

EXPO2011 is a new package for phasing crystal structures from powder diffraction diagrams. It is able to carry out all the steps necessary for crystal structure solution, from pattern indexation up to Rietveld method for structure refinement: for each step, the basic algorithm is described. Phasing is performed via ab initio (e.g., Direct Methods, integrated by real space refinement) and non ab initio techniques (e.g., simulated annealing algorithm, when molecular geometry is a priori known). Some emphasis is given to running procedures: the main commands and directives are described, to allow the user to run default and non-default phasing attempts.

Two-dimensional proportional detectors with their faster data collection, large dynamic range, and more available information than point or linear proportional detectors make them ideal for microdiffraction analysis. The unique capabilities of these detectors coupled with a rotating anode source, capillary optics, and a variety of accessories allow for a wide range of applications.

An instrument for the simultaneous measurement of X-ray powder diffraction (XRD) data and differential scanning calorimetry (DSC) data under a controlled humidity condition has been developed in order to achieve a design concept of reliable and simple in operation. Examples of the application to studies on hydration, dehydration, and rehydration processes of pharmaceutical compounds under various humidity conditions are presented. The usefulness of the present XRD-DSC system will be demonstrated.

Computer algebra removes much of the drudgery from mathematics; it allows users to formulate models by using the language of mathematics and to have those models evaluated with little effort. This symbolic form of representation is often thought of as being separate to dedicated computational programs such as Rietveld refinement. These dedicated programs are often written in low level languages; they are relatively inflexible in what they do and modifying them to change functionality in a small manner is often a major programming task. This paper describes a symbolic system that is integrated into the dedicated Rietveld refinement program called TOPAS. The symbolic component allows large functional changes to be made at run time and with a relatively small amount of effort. In addition, the system as a whole reduces the programming complexity at the developmental stage.

XRF is generally considered a nondestructive analytical method in the sense that a specimen is not altered by the analytical procedure. This study is related to paintings and illuminated manuscripts, where the analytes are often inorganic pigments embedded into organic matrices such as fabrics (canvases), paper or parchment, binders, and varnish. We found that a typical measurement cycle with conventional tubes and energy dispersive systems (e.g., 100 s, 100 W tube-power) causes no visible harm. However, 3 kW radiative power for several minutes and more (as often required for wide angle scans as well as for the analysis of light elements or traces in a wavelength dispersive spectrometer) can leave visible traces of permanent yellowing, brittleness, and even mechanical decomposition. In such cases scanning electron microscopy-images indicate permanent alteration of the cellulose fibers and, in paper, of the binder. Employment of modern X-ray optical devices which focus the photons of a wide beam onto a small spot may also leave visible (and invisible) traces of destruction.

The two mixed halides of barium, barium chloroiodide and barium bromoiodide, were synthesized via a solid-state reaction route. In this article, their powder XRD data are reported. A careful analysis of the X-ray data shows that both BaClI and BaBrI crystallize in the orthorhombic structure. The lattice parameters obtained are a=17.841±0.003 Å, b=8.441±0.001 Å and c=5.642±0.001 Å for BaClI (SG. Pbam, No. 55) and a=13.667±0.002 Å, b=12.012±0.001 Å and c=10.871±0.002 Å for BaBrI (SG. P2221 No. 17).

The peak profile shape analysis has been preferentially used in the evaluation of X-ray and synchrotron powder diffraction pattern. However, neutron diffraction facilities of new generation frequently offer the instrumental resolution high enough to efficiently study the effects of broadening of neutron diffraction profiles. The present paper describes the procedure for a detailed evaluation of Bragg peak shape based on the method of transformed model fitting (TMF) which has been recently developed particularly for the treatment of neutron diffraction profiles. Microstructure modeling is performed in the reciprocal space and the convolution of the model with the instrumental resolution curve is fitted to the profiles recorded in the diffraction experiment.

A novel porous material of composition Zn3(VO4)2⋅3H2O was prepared hydrothermally. The solid crystallizes in the hexagonal space group P6, with a=6.078 77(8), c=7.1827(2) Å, and V=229.857 Å3.

Ba(3−x)Srx(PO4)2 orthophosphates (0≤x≤3) have been prepared by solid state reaction. The final temperature was 1000°C. The X-ray diffraction analyses show the existence of a continuous solid solution. Ba(3−x)Srx(PO4)2 orthophosphates (0≤x≤3) crystallize in the hexagonal system with the space group R3m. Their structure is based on a three-dimensional framework constructed of infinite layers of Ba1/Sr1O12 linked and parallel to infinite layers of Ba2/Sr2O10 polyhedra and PO4 tetrahedra.