A method is described to determine the standard deviation of a peak position due to counting statistics. In this method, the statistical noise for a peak is first simulated based on the model of Poisson distribution and then imposed on the peak. The peak position is then determined by a profile fitting routine. By repeated application of these processes on a given peak, one obtains a number of slightly different peak positions and hence their corresponding standard deviation. This method can be applied to a peak described by any analytical function or a set of any number of digitized points. Investigation of the precision of peak positions was carried out by applying this method on various analytical peaks located at low, medium, and high 2θ angles. The results showed that the standard deviation of a peak position decreases with increasing P/B and P/σ, where P is the net peak count above the background B and σ=(P + B)½ is the estimated standard deviation for noise. It increases with increasing peak width and Δ2θ, the step size used to digitize the peak profiles. It decreases as the 2θ range of simulation and fitting increases up to 2θ=3 FWHMs (full width at half maximum) and remains at a constant value thereafter. The standard deviation of the position of a real peak obtained by ten repeated measurements is 0.0034°; the corresponding result obtained by the current method is 0.0035°. This peak is best fitted by a Pearson-VII function and the standard deviation obtained by this method is 0.013° when only the head portion with intensity ≥85% maximum net intensity is simulated and fitted. The corresponding result obtained by the traditional method of parabola fitting is 0.0055°. Therefore, the precision of a peak position also depends on the peak shape.

Ammonium nickel phosphate monohydrate (NH4NiPO4·H2O) crystal data were obtained by X-ray powder diffraction. Ammonium nickel phosphate monohydrate is orthorhombic with unit-cell parameters a = 5.566 (1) Å, b = 8.760 (2) Å, and c = 4.742 (1) Å.

Ab initio structure determination of new compound (Pb0.6Cu0.4)Sr2PrCu2O7−x was obtained at 300 and 100 K from X-ray powder diffraction data and refined by Rietveld technique. (Pb0.6Cu0.4)Sr2PrCu2O7−x has an isotypical structure with TlBa2CaCu2O7 (1212) at both 300 and 100 K. At 300 K, crystal data: (Pb0.522Cu0.4)Sr2PrCu206.53, Mr=681.293, tetragonal system, space group P4/lmmm, a = 3.8631(5)Å, c= 11.9134(2)Å, V= 177.79Å3, Z= 1, Dx, = 6.3631 g/cm3, μ=1036.549 cm−1 (λ=1.54051 Å), F(000) = 299.6, the structure was refined with 31 parameters to Rwp = 4.02%, Rp=2.96% for 3379 step intensities and Rb = 4.80%, Rf=5.17 for 143 reflections, “goodness of fit” S = 2.20. At 100 K, crystal data: (Pb0.547Cu0.4)Sr2PrCu2O6.89, Mr=692.232, tetragonal system, space group P4/mmm, a = 3.8580(2) Å, c= 11.8898(5) Å, Z=1, Dx = 6.4953 g/cm3, μ= 1053.235 cm−1 (λ=1.54051 Å), F(000) = 304.6, the structure was refined with 32 parameters to Rwp = 5.53%, Rp=4.22% for 2574 step intensities and Rb = 6.11%, Rf=5.31% for 111 reflection, “goodness of fit” S= 1.79. Moreover, the composition of Pb was refined to 0.522 at 300 K and to 0.547 at 100 K as compared with the stoichiometric composition 0.6.

The structure of [Pd(NH3)4]Cr2O7 has been determined ab initio from conventional X-Ray powder diffraction data by the Patterson method. The cell is monoclinic (space group P21/c, Z = 4), with a = 7.771(3) Å, b=11.578(1) Å, c=11.852(4) Å, and β= 105.50(4)°. Refinements of 57 parameters by the Rietveld method, using 852 reflections lead to RB = 0.032, RP = 0.075, and Rwp = 0.092. The structure is built up from PdN4 square planes linked to Cr2O7 groups by hydrogen bonds. Hydrogen atoms could not be located.

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

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).

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.

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 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.

X-ray powder diffraction data for the spinels CoAl2O4 and CoGa2O4 were measured with synchrotron radiation using λ = 1.2033 Å, determined with Si as a standard (a = 5.4305 Å). The two blue compounds prepared hydrothermally are cubic with space group Fd3m. Profile refinements gave the results: CoAl2O4 had a = 8.0968(1) Å and composition (Co0.71Al0.29]Al1.71Co0.29]O4 and CoGa2O4 had a = 8.3229(1) Å and composition Ga[CoGa]O4. The degree of inversion is thus 0.29 for CoAl2O4 and one for CoGa2O4.

The kieserite-type solid-solution series of synthetic (Cu,Mg)SO4·H2O was investigated by TG-analysis and X-ray powder diffraction using the Rietveld method. Representatives with Cu≥20 mol% are triclinic distorted () analogous to the poitevinite (Cu,Fe)SO4·H2O compounds. Cation site ordering with preference of Cu for the more distorted M1 site was additionally proven by the structure refinement.

X-ray powder diffraction data are reported for the trihydrated (A3N), the dihydrated (A2N), and the anhydrous ammonium trioxalatoaluminate (III) (AN). A3N is triclinic with space group . A2N and AN are monoclinic with space groups P21/c and P21/n respectively. The stability domains are A3N: –7.8 to 86 °C; A2N: 86 to 102 °C; AN: 102 to 180 °C.

A synthetic catalyst precursor formed by sulfiding ferrihydrite (Fe3+O(OH)) in the presence of a hydrogen donor produces X-ray diffraction patterns resembling a mixture of both naturally occurring FeS2 polymorphs marcasite and pyrite. The diffraction peaks display a differential broadening, however, wherein only those peaks coincident to both marcasite and pyrite are strong and sharp, a feature that cannot be accounted for by a simple physical mixture. The broadening is analogous to that found in hexagonal cobalt, where occasional stacking faults produce interstratification of the hexagonal and cubic close-packed forms, resulting in strongly coherent diffraction only along the stacking direction. The crystal structures of marcasite and pyrite are virtually identical if viewed perpendicular to the (101) and (001) planes, respectively. Calculation of diffraction patterns based upon models of interstratifying marcasite and pyrite layers along these planes demonstrates that a sequence with marcasite-to-pyrite and pyrite-to-marcasite stacking fault probabilities of 0.22 provides a good fit to the experimental pattern. This interstratified material is a precursor to a species that shows catalytic activity for cleaving C-C bonds between aromatic rings and benzylic carbon atoms at low (<350 °C) temperatures.

A new semi-empirical approximation for the asymmetry function to be used in the X-ray Rietveld analysis has resulted in lower values of the so-called goodness-of-fit index, defined as S = Rwp/Rexp, where Rwp is the R-weighted pattern and Rexp is the R-expected [R. A. Young, The Rietveld Method (Oxford U.P., Oxford, 1993)], with respect to the corresponding values obtained with the classical approximation used by Rietveld in his fundamental paper. A comparing test of the two asymmetry functions was carried out for the cubic Y2O3 and for αAl2O3 using either pseudo-Voigt or Pearson VII symmetrical functions and two diffractometers. As in the case of the Rietveld approximation, the present one, which employs an exponential function, is optimized using only one fitting parameter. Experimentally, the asymmetry can be considerably diminished by using Soller slits with a small opening angle (≤2°).

The X-ray powder diffraction pattern for the title compound is reported in the range 5 ≤ 2θ ≤ 125°. The sample was prepared through solid-state reaction of BaCO3, CuO, and Pr6O11, and characterized with respect to oxygen content through iodometric titration. Refined parameters for the orthorhombic (space group Pmmm) unit cell are a = 3.8587(2) Å; b = 3.9302(1) Å; c= 11.7126(3) Å; a/b = 0.98181(6); a/c = 0.32945(2); b/c = 0.33555(1); Z = 1; Dx = 6.705(2) Mg m−3; V = 177.62(1) Å3; formula wt. = 717.48(16) g mol−1; SS/FOM: F30 = 48(0.005,127).

I had just completed my BS in chemistry at Northwestern University in 1928 and had passed the Civil Service Chemistry Examination, and my fiance had passed an examination for the Civil Service Commission and had been offered a job at that agency in Washington. So we got on a train and came to DC, arriving 15 March 1928. I went to the Civil Service Commission (now called the Office of Personnel Management) and was directed to NBS where there were a number of openings for a P1 chemist. There I talked to Dr. Wichers in Chemistry and to J. Murray in the Lime and Gypsum Section. I took a job in the latter. On 31 March, we got married and on Monday, 2 April 1928, I started work in the Lime and Gypsum Section of the Clay and Mineral Products Division.

A wide range of transition metal oxide solid solutions have been prepared and characterised using powder X-ray diffraction (MnxCo1−xFe2O4, FexCo1−xFe2O4, NixCo1−xFe2O4, FeFexCr2−xO4, MnFexCr2−xO4, MnxFe1−xCr2O4, MnxFe1−xFe2O4, NixFe1−xFe2O4). Calibration curves have been obtained relating oxide composition to unit cell parameter or d spacing. From these curves it is possible to identify the composition of oxides formed on steel surfaces in varied industrial environments. Even when poor diffraction patterns are obtained and little sample is available, an estimate of composition can be made.

Based on the crystal structure determination of orthorhombic Ba2CuF6 (space group Cmca), the previous X-ray powder patterns given for Ba2CuF6 (PDF 21-809) and Pb2CuF6 (PDF 22-654) are reindexed.