Two new solubility-limiting phases relevant to nuclear waste disposal are reported, namely CeSiO4 and Ca2Ce8(SiO4)O2, produced by hydrothermal synthesis at 180 °C. X-ray diffraction data are presented for both compounds. Rietveld refinement was performed for each of these phases. CeSiO4 was confirmed to be a zircon structure type, with space group I41/amd, unit cell type="bold">abold=6.9564(3), type="bold">cbold=6.1953(4) Å. Bond lengths for SiO4 are in excellent agreement with published values; Ce4+ is coordinated to eight oxygen atoms with four regular and four short bonds. Ca2Ce8(SiO4)O2 was shown to have an apatite structure, with space group P63/m and unit cell type="bold">abold=9.4343(3), type="bold">cbold=6.8885(4) Å. The unit cell and bond lengths were found to be slightly smaller than would be expected from other lanthanide-containing analogs; possible reasons for this are discussed.

A cover for Scintag's six and twelve-position sample changers was designed and constructed to provide an inert atmosphere for samples during diffraction batch runs. The cover is equipped with inlet and outlet gas ports and fits over the top of the sample changer. Using dry nitrogen gas fed into the inlet of the cover, a sample of lithium bromide was protected from atmospheric moisture for greater than 18 h. The cover uses a thin Mylar window that gives greater than 95% transparency for copper K-alpha X-rays. The cover is a simple device that allows our lab to run multiple moisture-sensitive samples in a batch mode. The simple approach and materials used in the construction of the cover could be applied to other brands of powder diffractometers.

We report precision X-ray powder-diffraction (XRD) data of single phase pure Ti2ZrAl. Ti2ZrAl samples were prepared by an arc melting method and annealed at 1000 °C for 30 days. XRD analysis was carried out on these samples and it was found that Ti2ZrAl has a DO19 structure (space group P63/mmc, No. 194). The lattice parameters are found to be a=5.961±0.001 Å and c=4.793±0.001 Å.

As is well known from literature, the grinding process, which is an unavoidable step in sample preparation, may strongly modify the physical properties of chrysotile through amorphisation. The aim of this work is to establish the proper milling time to apply to the samples before an accurate X-ray powder diffraction quantitative analysis. We have used the RIR (reference intensity ratio) analytical method, based on the measurement of the ratio I/Is between the intensity of the strongest line of an analyte and the intensity of the analytical peak of a standard material, when they are thoroughly mixed 50:50 by weight. We have studied how the RIR value changes as a function of the milling time of the sample and how the accuracy of this quantitative method is affected.

In this paper we present a high temperature heating device, working under defined environmental conditions, for a Siemens D500 Bragg–Brentano powder diffractometer. The powder sample is prepared in a flat mould on a metal block consisting either of copper or of platinum depending on the temperature range selected for investigations. Although the heating cell can be used separately under ambient conditions up to sample temperatures of 1000 °C, it is possible to work under defined environmental conditions in the temperature range between 20 and 200 °C and up to a water vapour pressure of 1000 mbar. For that purpose a special cover for the in situ control of temperature and water vapour pressure has been constructed. It is important to note that the three sample conditions (sample temperature, gas temperature, and gas humidity) can be adjusted separately by the user. Current studies have shown that the described X-ray heating device is a powerful tool to study dehydration reactions in the frame of fundamental research as well as to understand industrially relevant processes concerning dehydration reactions and their mechanisms.

Aluminum borate (9Al2O3·2B2O3) whiskers were chemically synthesized in potassium sulphate flux by using the starting chemicals of aluminum sulphate and boric acid. The synthesis temperature of 1075 °C was found to be the optimum with respect to whisker morphology. A tentative X-ray diffraction (XRD) pattern was suggested for the whiskers produced after heating at 1150 °C. The product purity, phase composition, and whisker morphology were investigated by XRD, energy dispersive X-ray spectroscopy, and scanning electron microscopy, respectively.

Arsenic molybdate, As2MoO7, produced by phase transformation of As4Mo3O15, has been analyzed by X-ray powder diffraction. The powder diffraction data were collected with a focusing (Guinier-type) transmission diffractometer equipped with a primary-beam monochromator (Ge 111) for Cu Kα radiation and a scanning position-sensitive detection system. A monoclinic unit cell was determined using an indexing program and compared with calculated single crystal data.

Powder diffraction data were collected for a synthetic zinc molybdate of composition Na(OH)Zn2(MoO4)2·2.5H2O. The material is monoclinic, space group C2/m, with a=9.4543(12), b=6.3492(7), c=7.6453(11), β=115.899(13), and V=412.83 Å3.

A special computer storage method for chemical structures is illustrated in this article. With an improved method of two-dimensional connection table and topology, we can fit almost all chemical structures and display them very conveniently. We have used this method in the PDF (X-Ray Powder Diffraction File) database, which contains many special structures.

Key words: database, computer application, chemical structure

Powder X-ray diffraction data of melatonin C13H16N2O2 were collected on a conventional X-ray powder diffractometer: the monoclinic cell parameter are a=7.7416(8) Å, b=9.2897(9) Å, c=17.1444(16) Å, β=96.756(9)°, volume 1224.4(3) Å3 (space group P21/c). The strongest lines are (d (Å), I/I0) 8.161 (100), 5.411 Å (46), 3.412 Å (34), 4.668 Å (33), 4.645 Å (25), 3.554 Å (22), 3.668 Å (16), and 4.483 Å (14). Reported intensities are validated by Rietveld analysis. The data consist of measured positions and intensities and cover an angular range up to 60° 2θ: experimental, calculated, and difference patterns are also reported.

A complete set of d spacings, intensities, and h, k, l indexes for Ti2AlN has been determined from X-ray powder diffraction. The lattice parameters are a=2.989(2) Å, c=13.614(5) Å; in good agreement with previous work. The new set of results comprises seven reflections not present in the current Ti2AlN PDF card No. 18-70. Furthermore, a new set of relative intensities are reported that are in better agreement with the calculated values than they are with those listed in the PDF card.

The titled compound, Hg2[Fe(CN)5NO], was synthesized and studied by X-ray powder diffraction, infrared spectroscopy, Mössbauer spectroscopy, and atomic force microscopy. The results arising from this study indicate that this compound is anhydrous and crystallizes in the P222 orthorhombic symmetry. The unit cell parameters were quantified as a=16.5905(9) Å, b=12.3145(8) Å, and c=8.7576(5) Å. The measured and calculated density values are Dm=1.149 g/cm3 and Dc=1.145 g/cm3, respectively, with Z=2.

A critical examination of the reference X-ray powder-diffraction patterns of the serpentine minerals in the Powder-Diffraction File (PDF) database has revealed an unsettling situation. Most of the patterns in, or previously in, the PDF database are inaccurate, misidentified, or of poor quality. The PDF database is not a dependable tool for identifying the serpentine minerals, and has not been since the mid-1960s. This has serious implications for studies on serpentine minerals that have depended on the PDF database, particularly those by nonmineralogists doing health and environmental studies of chrysotile asbestos. In the current PDF database, lizardite-1T, carlosturanite, some amesite, and possibly some antigorite (but with inappropriate polytype symbols) can be identified. Only one of the many multilayer lizardites can be identified. The current pattern for chrysotile-2Mc1 (clinochrysotile) is of reasonable quality, but not the best, however the earlier patterns still in the database are so problematic that any chrysotile-2Mc1 identification must be considered suspect. Chrysotile-2Oc1 (orthochrysotile), and any mixture of serpentines cannot be identified using the PDF database. Until the reference serpentine patterns are corrected the PDF database cannot be considered a reliable identification tool. High-quality powder-diffraction patterns of the serpentine minerals have been published and can be rapidly introduced into the PDF database.© 2000 International Centre for Diffraction Data.

New powder X-ray diffraction data of adenosine C10H13N5O4 were reported: cell parameters are a=4.8386(4) Å, b=10.2919(4) Å, c=11.8555(4) Å, β=99.298(5)°, volume 582.63(4)Å for the monoclinic space group P21. The strongest lines are: 7.723 (100), 5.085 (50), 5.851 (45), 4.710 (11), 3.881 (10), 3.899 (9), 3.292 (9), and 3.261 (9). Reported intensities are validated by Rietveld analysis. The data consist of measured positions and intensities and cover an angular range up to 75° 2θ and are significantly better than PDF 35-1977. Experimental, calculated, and difference patterns are also reported.

Powder X-ray diffraction data are reported for semimagnetic semiconductor Hg0.89Fe0.11S and Hg0.98Co0.02S crystals grown by the Bridgman method and for Hg0.80Mn0.20S crystal synthesized by a solid-state reaction method. The crystals have the sphalerite structure of metacinnabar (sphalerite-type high-temperature polymorph of HgS, space group F4¯3m). Phase analysis does not show any trace of other phases. The lattice parameters of the studied samples are a=5.803 20(5) Å, 5.8063(1) Å and 5.839 80(6) Å, respectively. The calculated density is reported.

A chemical and mineralogical investigation of a Moroccan pyrophyllite is presented. X-ray powder diffraction has been largely used for phase identification and crystal symmetry determination. It is shown that this mineral has a triclinic symmetry with cell parameters: a=5.160 Å, b=8.993 Å, c=9.360 Å, α=90.77°, β=100.57°, and γ=89.71°.