Leucites are tetrahedrally coordinated silicate framework structures with some of the silicon framework cations that are partially replaced by divalent or trivalent cations. These structures have general formulae A2BSi5O12 and ACSi2O6, where A is a monovalent alkali metal cation, B is a divalent cation, and C is a trivalent cation. There are also leucite analogs with analogous tetrahedrally coordinated germanate framework structures. These have general formulae A2BGe5O12 and ACGe2O6. In this paper, the Rietveld refinements of three synthetic Ge-leucite analogs with stoichiometries of AAlGe2O6 (A = K, Rb, Cs) are discussed. KAlGe2O6 is I41/a tetragonal and is isostructural with KAlSi2O6. RbAlGe2O6 and CsAlGe2O6 are $I\bar{4}3d$ cubic and are isostructural with KBSi2O6.

A novel algorithm has been developed for obtaining directly the applicable indices hkl for any interplanar spacing, dobs±Δdobs, of a triclinic phase with known unit cell parameters. This method is particularly useful for indexing back reflections for triclinic phases with unit cell volumes greater than 500 Å3.

Standardized X-ray powder diffraction data for orthorhombic LaCo0.4Fe0.6O3 prepared by calcination of a glycine-nitrate combustion-synthesized precursor are reported. Orthorhombic unit cell parameters: a = 5.4688 (2), b = 5.5100 (2), c = 7.7462 (3) Å. The reference intensity ratio, I/Icor,= 6.12.

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.

Methods using X-ray fluorescence have been developed to identify cometary material captured in aerogel during the NASA Stardust mission to Comet 81P/Wild 2. These analytical methods are necessitated by the levels of trace contaminants present in the aerogel. The cometary material disaggregates during deceleration in the aerogel, so fluorescence mapping of the entire track (which can be several millimeters long) is necessary. Distinguishing those pixels which have cometary material and aerogel from those which have only cometary material can be very challenging. We have chosen a “dual threshold” method, with some pixels clearly having only aerogel (plus contaminants) and other pixels clearly having cometary and aerogel material. Between these two threshold levels is a set of pixels which cannot be easily ascribed to one or the other. By leaving these pixels out of the analysis, the estimate of cometary material is improved.

Nickel oxide nanopowder was prepared by a simple method and analyzed by X-ray powder diffraction. A solution of gelatin and NiCl2⋅6H2O salt were prepared and sintered in sequence. Using a synchrotron light source for X-ray powder diffraction analysis, the synthesized material was characterized as a function of temperature in the interval of 375 to 600 °C. Results from thermogravimetric analysis confirm the temperature loss of the organic substance during the sintering process and show that the temperature for NiO attainment is 600 °C.

The X-ray powder diffraction patterns for two N-substituted tetrahydroquinolines are reported. N-(α-Chloroacetyl)-6-methoxy-3,4-dihydro-4-methylspiro[cyclohexane-1′,2(1H)quinoline], C18H24ClNO2, and N-(α-chloroacetyl)-6-chloro-3,4-dihydro-4-methylspiro[cyclohexane-1′,2(1H)-quinoline], C17H21Cl2NO are monoclinic, with refined unit cell parameters a=1.4471(3), b=0.9600(4), c=1.1948(3) nm, β=93.21(2)°, V=1.6573(6) nm3, Z=4, Dx=1.29 gcm−3, and a=1.4487(3), b=0.9878(2), c=1.1390(2) nm, β=91.66(2)°, V=1.6294(4) nm3, Z=4, and Dx=1.32 gcm−3, respectively, with space group P21/n (No. 14).

Key words: powder diffraction data, spirotetrahydroquinolines.

A monoclinic phase isostructural to Al4W was revealed in Al–Ni–Re close to the Al–Re terminal. It is assumed to be a ternary extension of the high-temperature Al4Re phase usually transforming in binary alloys even by sharp quenching from the existence temperatures. The powder X-ray diffraction pattern of this phase of the Al77Ni2.5Re20.5 composition was indexed for the Cm space group with a=5.1538(12) Å, b=17.410(5) Å, c=5.1546(15) Å, and β=100.548(16)°.

The National Institute of Standards and Technology (NIST) certifies a suite of Standard Reference Materials (SRMs) to address specific aspects of the performance of X-ray powder diffraction instruments. This report describes SRM 1879b, the third generation of this powder diffraction SRM. SRM 1879b is intended for use in the preparation of calibration standards for the quantitative analyses of cristobalite by X-ray powder diffraction in accordance with National Institute for Occupational Safety and Health (NIOSH) Analytical Method 7500, or equivalent. A unit of SRM 1879b consists of approximately 5 g of cristobalite powder bottled in an argon atmosphere. It is certified with respect to crystalline phase purity, or amorphous phase content, and lattice parameter. Neutron powder diffraction, both time-of-flight and constant wavelength, was used to certify the phase purity using SRM 676a as an internal standard. A NIST-built diffractometer, incorporating many advanced design features was used for certification measurements for lattice parameters.