A new amine zinc hydroxide nitrate has been synthesized and investigated by means of X-ray powder diffraction. The monoclinic unit cell dimensions are a = 20.781(3) Å, b = 6.2151(9) Å, c = 5.4952(6) Å, β = 92.24(1)° (space group C2/m with Z = 2). The crystal structure has been refined by the Rietveld method using the structure of the related dihydrated phase as a starting model (Rp = 0.092 and RF = 0.068 for 372 reflections). The structure is characterized by octahedra [Zn(OH)6] describing a brucite-type layer, with one-quarter of the metal atoms missing, and by tetrahedra [Zn(OH)3(NH3)] located above and below the empty octahedra. The complex positive sheet has the formula [Zn3octa(OH)8Zn2tetra(NH3)2]2+ and the cohesion of the structure is realized through hydrogen bonding.

The crystallographic data of YBa2Cu3O7−δ, Y2BaCuO5, BaCu2O2, and YBa4Cu3O9 at high temperatures and p(O2)<10 Pa have been derived on the basis of HT-XRD measurements. Whereas Y2BaCuO5 expands nearly isotropically, YBa2Cu3O7−δ and BaCu2O2 show anisotropic expansions. Furthermore, the first decomposition step of the considered compounds at p(O2)<10 Pa was observed. BaCu2O2 melts congruently at T ≍ 1273 K and Y2BaCuO5 decomposes via a peritectic reaction into Y2O3, Y2BaO4 and melts at T ≍ 1323 K. A solid-state reaction into Y2BaCuO5 and BaCu2O2 was indicated for YBa2Cu3O7−δ at T ≍ 1123 K. Because YBa4Cu3O9 becomes unstable at T ≍ 1123 K, this compound cannot be formed by the primary decomposition reaction of YBa2Cu3O7−δ

Space group and unit-cell parameters for three 10,11-dihydro-5H-dibenz[b,f]azepine antidepressant drugs were determined. Indexed powder diffraction data for each drug are reported.

An X-ray powder-diffraction pattern for boracite, Mg3B7O13Cl, is reported. Boracite is orthorhombic, space group Pca21, and the refined unit-cell parameters are a=8.557(6), b=8.553(8), c= 12.09(1) Å. X-ray powder-diffraction patterns have been calculated for the boracite-group minerals boracite, ericaite, trembathite and congolite. The calculated pattern for boracite is in good agreement with the observed pattern reported here, but the PDF entry (5-710) for boracite is missing several intense peaks. The calculated pattern for ericaite is in poor agreement with the PDF entry (29-697) for ericaite, and PDF 29-697 is for congolite, not ericaite. The calculated powder patterns presented here for these four minerals will facilitate their identification via X-ray powder diffraction. © 1995 International Centre for Diffraction Data.

The measurement of x-ray diffraction line intensities is the basis for quantitative phase analysis (see for example, Chung (1974), Davis (1986), and Hubbard and Snyder (1988)). While there are many sources of error in such measurements, in recent years computer automation of powder diffractometers and associated analytical software has made such measurements more practical and accurate. For example, profile fitting software has made it possible to determine integrated peak areas and to deconvolute overlapping lines. Another problem which affects quantitative analysis is the systematic error in instrument sensitivity as a function of 20 diffraction angle. This effect has been partially responsible for poor reproducibility of relative intensities between laboratories (Schreiner and Kimmel (1987), and Jenkins and Schreiner (1989)). But, because the error is systematic, corrections may be made by using a standard such as the National Institute of Standards and Technology SRM 1976 alumina plate (NIST 1991). These and other advances have led to a renewed interest in the determination of I/Ic (also called RIR - Reference Intensity Ratio) values for crystalline substances (e.g., Snyder (1992)). I/Ic is defined as the ratio of the intensity of the strongest line of an analyte to the corundum (113) line when the analyte is mixed 50:50 by weight with corundum. We present here a standard procedure used in our laboratory to experimentally measure I/Ic values, and which explicitly incorporates profile fitting and instrument sensitivity corrections. The procedure is written in the format of an ASTM (American Society for Testing and Materials) standard test method, however, inter-laboratory round robin tests have not been carried out to determine precision and bias associated with the method. While the method calls for corundum as the internal standard, another standard material, s, may be used, in which case the procedure will result in a ratio I/Is. Hubbard and Snyder (1988) have shown how to convert between I/Is and I/Ic. This method is based on the procedure routinely published in NBS Monograph 25 until 1986. It is augmented with corrections for the angularly dependent instrument sensitivity and with calculations of I/Ic for both variable and fixed divergence slit configurations. A Quattro Pro spreadsheet is used in our laboratory to do the calculations. An example of the spreadsheet is given in the appendix for one of two I/Ic runs of MgCO3. We also utilize the corundum in the I/Ic runs as an internal standard to determine displacement error corrections for preparation of digitized patterns of pure analyte phases. These patterns are submitted to the International Centre for Diffraction Data for inclusion in a whole pattern data file planned for some time in the future. The notation used here is the standard notation developed for the RIR method by Hubbard and Snyder (1988) and systematically extended by Snyder (1992). A table of the notation is given in the Terminology section below.

Powder X-ray diffraction data for cubic La0.3Sr0.7CoO3−δ, perovskite prepared by a combustion method, using metal-EDTA complexes are reported. The cubic cell parameter is: ac = 3.8323(9)Å.

Powder-diffraction data were collected for a Chinese sample of ferrimolybdite. This mineral is orthorhombic, space group Pmmn or Pm21n, with a = 6.665(2), b = 15.423(5), c = 29.901(8), and V = 3074(1) Å3.

A technique is presented utilizing an unmodified commercial X-ray diffractometer, equipped with a Bragg–Brentano geometry, for reducing preferred orientation effects in measured intensities during quantitative diffraction analysis. The diffractometer setup examined makes possible data acquisition with Θ fixed at 1° and 2Θ scanning the Bragg line. The results obtained with this technique are shown in the quantitative X-ray diffraction analysis of three international standards of carbonate rocks (401,402,403).

DISVAR93 is a collection of programs devised to process XRPD patterns with the aim of determining the parameters of systematic instrumentation and sample effects. These effects have an influence on data uncertainty and also accuracy of the adopted models describing diffraction phenomena. Such modeling is carried out through the mathematical X-ray powder-diffraction theory, while parameter optimization is achieved by using the additive property of X2 and constraining the models to converge simultaneously to the same minimum in a restrained Hilbert's space. The package has been designed to allow both user interaction as well as automatic linking of programs managed by one main menu and offer several options to satisfy individual user requirements.

Detailed procedures for solving small crystal structures ab initio with the maximum-entropy (ME) methods using X-ray powder diffraction data are described by determining the structure of the low-pressure phase of magnesium boron nitride, Mg3BN3(L), which was previously solved by one of the authors and co-workers using the Patterson method and the direct methods. The simple ME method devised by Gull, Livesey, and Sivia failed to correctly phase the structure-factor data, leading to noninterpretable electron-density maps. This method, maximizing the entropy under the constraints of the observed structure factors with subsequent incorporation of strong extrapolates in the basis set, trapped the solution in a local entropy maximum, from which there is no way to move. The multisolution method of phase determination by entropy maximization and likelihood evaluation, developed by Bricogne and Gilmore, successfully located all the Mg, B, and N atoms in one cycle of phase extension. The correct solution had a highest log-likelihood gain, but a minimum entropy, among the multisolutions generated by phase permutation.

New powder X-ray data for cancrinite [ideally Na8Si6Al6O24 (CO3)2·2 H2O] are reported along with in-situ real-time thermal processes recorded using energy dispersive X-ray diffractometry (EDXD). A completely anhydrous phase is obtained after heating the sample up to 600 °C and quickly cooling it to room temperature, as shown by means of both Rietveld analysis and IR spectroscopy. The anhydrous phase does not show any tendency to re-acquire molecular water. During the heating process, at around 450 °C, a peak splitting is observed, possibly due to a reversible phase transition.

Icosahedral boron phosphide (B12P2) was directly synthesized from elemental powders by a high-temperature reaction under an argon pressure. Powder diffraction data were collected for two B12P2 samples, and diffraction patterns were compared with calculated patterns of phosphorus deficient crystals: B12+xP2−x for 0<;x<0.2. The as-synthesized B12P2 appears to be close to its ideal stoichiometry based on the consistency between the observed and the calculated values of the relative intensity for all diffraction planes below 90° 2θ.

Synthesis of high-purity, single-phase gallium nitride (GaN) powder has been achieved by reacting molten Ga with flowing ammonia (NH3) in a hot wall tube furnace. The optimum temperature, NH3 flow rate, and position of the boat in the hot wall tube furnace relative to the NH3 inlet for the complete reaction to pure GaN for our system were 975 °C, 400 standard cubic centimeters per minute (seem) and 50 cm, respectively. The X-ray diffraction (XRD) data revealed the GaN to be single phase with a = 3.1891 Å, c = 5.1855 Å, in space group P63mc, Z=2 and Dx =6.089 g cm−3. Scanning electron microscopy revealed a particle size distribution in the crushed material between 1 and 5 μm with most of the particles being ≍1 μm.

New solid solution phases in the (Y,Ca)(Cr,Co)O3 system have been synthesized and characterized by powder X-ray diffraction. The selected compositions in this system were prepared by the modified Pechini method. Powder-diffraction patterns were prepared.

X-ray powder diffraction data for Dichloro [bis(2-diphenylphosphinoethyl) phenylphosphine] [dimethylsulfoxide] Ruthenium (II) is reported. The powder pattern was obtained using CuKα radiation. The lattice parameters determinated by least-squares refinement for the monoclinic space group P21/c are: a = 21.073(3) Å, b = 11.970(2) Å, c = 16.889(3) Å, and β = 107.72(1)°, with M20 = 10.67 and F30 = 15.4 (0.0145, 134), and are in good agreement with those obtained from the single crystal structure determination. Observed and calculated X-ray powder diffraction data are given for the titled compound.

The quantitative analysis of carbonate rich materials is tested with conventional and Rietveld methods. In the case of artificial mixtures of aragonite, calcite, Mg-calcite and quartz the Rietveld method provides reliable results with a maximum deviation of ±5 wt %. In the natural samples, however, the conventional methods give more reliable results in comparison to chemical and sedimentological measurements. This is caused by the peak overlap of calcite/Mg-calcite, peak roadening of the Mg-calcite, and the difficulties in the refinement of minor amounts of feldspar phases.

The kalipyrochlore (K,Sr,Na,Ca,H2O)2−m(Nb,Ti)2−xO6−wY1−n, with (0<m<0.8, x∼0.2, w = 0 and 0.2<n<1) from Lueshe, Zaire is a defect pyrochlore species whose A-site weakly depleted. The measured powder diffraction is presented with a calculated figure of merit F(30) = 74.7(0.010,39). The structure has been refined by single-crystal from X-ray diffraction data collected on a Huber four-circle diffractometer and by Rietveld analysis from X-ray powder diffraction data. The slightly weathered crystal (studied by single crystal) has a cubic pyrochlore-type structure with the same atomic positions and a unit-cell parameter a = 10.603(5) Å, space group (S.G.): Fd3m. The highly weathered crystal (studied by Rietveld) has the same cubic pyrochlore-type structure except for the oxygen position. The oxygen moved from the 48f position with x, y, z equal to 0.284, 0, 0 to x = 0.308(5), y = 0.024(6) and z = –0.028(9). The cell parameter is a = 10.569(6)±0.0007 Å. These modifications of positions induce a distortion of the A-site into an hexagonal bipyramid and an elongation of the B-site along the c axis of the octahedron.

Because of their potential to induce a number of pathological diseases and their widespread industrial usage in the past, the fibrous minerals forming asbestos have been the subject of a number of studies in the past. Although quantification of asbestos minerals by optical and electron microscopy (SEM, TEM) is a routine technique in the case of dispersed airborn fibers, the detection and the quantification of small amount of fibrous minerals like chrysotile in bulk materials such as building materials is exceedingly difficult. A method for the detection and evaluation of asbestos minerals in massive samples is described, based on a combination of Rietveld and RIR (Reference Intensity Ratio) methods. Lower detection limits are about 0.5-1.0 wt % for chrysotile, depending on powder pattern, counting statistics, and matrix absorption. The chrysotile wt % determined on powder diffraction profiles collected on a conventional instrument is precise to about 1.0 wt % absolute (relative error in the range 0-10%). The technique is of straightforward application. If compared with the commonly used microscopic or spectroscopic techniques, it is of much advantage from the point of view of time, and the results are more accurate and statistically significant of the bulk material. A model for the cylindrically disordered structure of fibrous chrysotile is especially developed for the simulation of the X-ray powder patterns, and it is proposed here.

A nonlinear optical material 3-nitro–4-hydroxy–4′-bromobenzophenone 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 109 observed reflection with 2θ up to 90° are reported. The powder diffraction data have been evaluated, and the figures-of-merit are reported. The unit cell parameters least-squares refined from 34 nonoverlapping peaks of the orthorhombic compound with a P212121 space group are a = 7.619(7) Å, b = 27.651(5) Å, c = 5.650(7) Å, V = 1190.5(9) Å3, Z = 4, and Dx = 1.389 g/cm3.

The crystal structure of the tysonite-type superstructure of β-PrF3 has been studied by X-ray powder diffraction and high-energy electron diffraction from single crystals. The crystal data are: a = 7.0795(1) Å, c = 7.2380(2) Å, Z = 6, hexagonal system, space group (No. 165), ρcalc = 6.28 g cm−3. Atomic parameters and interatomic distances are presented from the final refinement with Rconv = 1.72%.