The ferroelectric liquid crystal material [4-[(4-methyloxyfenyl) carbonyloxyl] bifenyl-4′-yl]-(S)-2-methylbutoxypropionate containing a lateral methyl group on the aromatic ring of the alkoxybenzoate unit and two chiral carbons has been investigated by X-ray powder diffraction analysis at the 28 °C–105 °C temperature range. On cooling through the SmC temperature range, the layer spacing decreases from 28.3 to 27.7 Å with a small variation of average intermolecular distances. Lattice parameters of tetragonal and monoclinic crystalline phases occurring at lower temperatures have been determined.

A poster session was held during the Annual Spring Meeting of the International Centre for Diffraction Data on 20 March 2002. Abstracts of the posters are reproduced in the following. The underlined authors can be contacted for more information.

Data for the standard material NBS SRM 674, TiO2, were collected on two diffractometers: a) a Philips PW 1050/37 standard diffractometer of the Bragg-Brentano type equipped with a post diffraction curved Ge monochromator, b) a Stoe Stadi P diffractometer of transmission type equipped with a curved incident beam Ge monochromator. Both monochromators were set to select pure CuKα1 radiation. The reflection type instrument gives a much larger peak to background ratio than the transmission instrument, for which the background is much higher than with the reflection instrument. Rietveld refinements were carried out on both data sets with the programs DBWS-9807 and general structure analysis system (GSAS). The structural parameter of the oxygen atom of rutile depends neither on data set nor program, whereas, e.g., thermal displacement parameters seem to depend on both data set and program.

The atomic displacement parameters of individual ions in SrO have been determined from the Rietveld analysis of high-resolution powder neutron diffraction data. As the neutron velocity is smaller than the sound velocity in SrO, the intensity data was not corrected for the effect of thermal diffuse scattering. The room temperature value of overall isotropic thermal displacement parameters was B=0.57(2) Å2; which corresponds to Debye temperature, Θ of 242(4) K. The results are compared with experimental and theoretical estimates.

Silver sulfide, Ag2S, is most commonly known as the tarnish that forms on silver surfaces due to the exposure of silver to hydrogen sulfide. The mineral acanthite is a monoclinic crystalline form of Ag2S that is stable to 176°C. Upon heating above 176°C, there is a phase conversion to a body-centered cubic (bcc) form referred to as argentite. Further heating above 586°C results in conversion of the bcc phase to a face-centered cubic (fcc) phase polymorph. Both high-temperature cubic phases are solid-state silver ion conductors. In situ high-temperature X-ray diffraction was used to better understand the polymorphs of Ag2S on heating. The existing powder diffraction file (PDF) entries for the high-temperature fcc polymorph are of questionable reliability, prompting a full Rietveld structure refinement of the bcc and fcc polymorphs. Rietveld analysis was useful to show that the silver atoms are largely disordered and can only be described by unreasonably large isotropic displacement parameters or split site models.

Methods of chemical preparation and crystallographic data are reported for two new condensed phosphates: a polyphosphate of nickel and cesium, NiCs4(PO3)6, and a cyclotriphosphate of nickel and potassium, NiK4(P3O9)2. NiCs4(PO3)6 is rhombohedral with the following unit-cell dimensions: a=b=11.602(1) Å, c=9.078(1) Å, space group P−31c, V=1058.24(1) Å3, and Z=2. NiK4(P3O9)2 is triclinic with the following unit-cell dimensions: a=6.143(8) Å, b=6.80(1) Å, c=12.80(3) Å, α=102.8(3)°, β=89.7(2)°, γ=66.03(7)°, space group P−1, V=473.56(3) Å3, and Z=1.

Crystal structures of types II and III chlorothalonil, 2,4,5,6-tetrachloro-1,3-dicyanobenzene, (C8Cl4N2) were solved by applying Monte Carlo simulated annealing techniques to X-ray powder diffraction data and refined using the Rietveld method. Both types of chlorothalonil crystallize in monoclinic symmetry (space group P21 and two molecules per unit cell). Lattice parameters are: a=8.1615(18) Å, b=9.4191(19) Å, c=6.4728(14) Å, β=93.7307(64)° and V=497.8 Å3 for type II, and a=8.6003(10) Å, b=9.2382(11) Å, c=6.3024(7) Å, β=96.2152(60)° and V=498.5 Å3 for type III. The structures of both types of chlorothalonil are stacked by two coplanar molecular sheets paralleled to the b-axis. The adjacent two paralleled molecules in type II are on the same plane, while those in type III are on two different parallel planes.

The crystal structure of a series of substituted sulfonylureas were studied in this paper by means of powder diffraction, and the cell dimensions of each compound were refined by a least squares analysis. The cell parameters were in good agreement with those obtained from single crystal data. © 2002 International Centre for Diffraction Data.

Ba0.5Sr0.5TiO(C2O4)2·5H2O, which is used as a precursor for Ba0.5Sr0.5TiO3 (BST), has been characterized by X-ray powder diffraction. In accordance with the known structure of BaTiO(C2O4)2·yH2O, the crystal system was found to be monoclinic with unit cell parameters: a=1.3965(1) nm, b=1.3811(2) nm, c=1.3306(2) nm, and β=92.15(1)°. The space group is P21/n, ρ=2.292(2) g cm−3, and Z=8.

X-ray diffraction techniques have been applied to study the crystallization of poly(ethylene-2,6-naphthalate), PEN. Uniaxial and biaxial orientation of amorphous cast PEN films resulted in stress-induced crystallization of the triclinic α-PEN polymorph. Annealing of the amorphous PEN samples in the range of 160–240 °C produced thermally induced crystallization of α-PEN. Slow cooling of amorphous PEN from the melt state generated α-PEN as well as the triclinic β-PEN polymorph.

X-ray diffraction methods have been used successfully for the analysis of platinum silicide films of 100 Å or less in thickness. Conventional X-ray diffraction was utilized for phase identification, planar orientation, and crystalline size determination. Low-angle X-ray specular reflectivity analysis measured film thickness. As the nominal film thickness approached 100 Å, it was observed that the deposited platinum film thickness was larger than expected and longer anneal times would be required to ensure homogeneous platinum silicide phase composition.

Ternary Al–Ni–Pt phase isostructural to Al28Ir9 was revealed at the Al74Ni7.2Pt18.8 composition. Its powder diffraction pattern was indexed for the space group P31c (No. 159) and lattice parameters a=12.095(8) and c= 26.922(17) Å.

N-derivatives of 4-chloro-3,5-dimethylphenoxyacetamide—2-(4-chloro-3,5-dimethylphenoxy)-N-(4-fluorophenyl)acetamide, 2-(4-chloro-3,5-dimethylphenoxy)-N-(3-chloro-4-fluorophenyl) acetamide, 2-(4-chloro-3,5-dimethylphenoxy)-N-[4-chloro-3-(trifluoromethyl)phenyl] acetamide, 2-(4-chloro-3,5-dimethylphenoxy)-N-[3-chloro-4-methylphenyl]acetamide, 2-(4-chloro-3,5-dimethylphenoxy)-N-(2,4,6-tribromophenyl) acetamide, 2-(4-chloro-3,5-dimethylphenoxy)-N-pyridin-2-ylacetamide, 1-[(4-chloro-3,5-dimethylphenoxy)acetyl]-4-methylpiperazine, and 1-benzyl-4-[(4-chloro-3,5-dimethylphenoxy)acetyl]piperazine—have been characterized by X-ray powder diffraction. These organic compounds are potential pesticides. Experimental 2θ peak positions, relative peak intensities, values of d and Miller indices, and unit-cell parameters are presented.

Pr1+xBa2−xCu3O7±δ solid solution was investigated by means of X-ray powder diffraction and Rietveld analysis. Single-phase PrBa2Cu3O7±δ (Pr123) can be synthesized under a Pr-rich condition by sintering at 950 °C in air. The solubility of Pr1+xBa2−xCu3O7±δ solid solution is 0.08≤x≤0.80. The structure of Pr1+xBa2−xCu3O7±δ is orthorhombic for 0.08≤x<0.30, and transforms into tetragonal for 0.30≤x≤0.80. To form single-phase Pr123, the Ba sites in the Pr123 structure are partially occupied by excess Pr ions, and the smallest amount of excess Pr is x=0.08. Meanwhile, all Ba ions stay in the Ba sites.

X-ray powder diffraction is one of the two principal methods used for the routine analysis of free SiO2 for monitoring silica in the industrial workplace. During late 1996 and early 1997, a questionnaire was prepared and distributed to all the analytical laboratories on the American Industrial Hygiene Association (AIHA) list of accredited facilities that indicated they did analyses for silica. This report is based on the responses to that questionnaire with comments from the author on the responses and recommendations that suggest themselves from the responses.