The anhydrous and hydrated lithium monoborates have been studied. The most hydrated phase is LiBO2·8H2O; its structural formula in the P3 space group is Li(H2O)4B(OH)4·2H2O. Refinement of the cell parameters yielded the following results: a=6.5483(5) Å, c=6.1692(7) Å with F(30)=64(0.015, 32), Z=1, and Dx=1.402 g/cm3. This phase gives LiB(OH)4 by spontaneous dehydration. An X-ray powder diffraction study of LiB(OH)4 as a function of temperature indicated three poorly crystallized hydrates. Two of these hydrates have the formula LiBO2·0.3H2O; the other, LiBO2·xH2O, has an undetermined water content. Crystal data for α-LiBO2 have been obtained: a=5.8473(10) Å, b=4.3513(6) Å, c=6.4557(10) Å, β=115.08(1)°, F(27)=58.5(0.001, 41); space group P21/c, Z=4, and Dx=2.18 g/cm3. β-LiBO2 does not exist but corresponds to the α-LiBO2 form observed at 600 °C. Numerous other LiBO2 forms reported recently have not been found.

The Debye-Scherrer technique and filtered Cu Kα, radiation were used to obtain powder data for reflections to an angle of 2θ = 155°; a vertical scanning diffractometer was used to obtain intensity data to an angle of 2θ = 99°. The space group is with Z = 4. The lattice parameters of the tetragonal unit cell were measured to be a = 6.189 (1) Å and c = 12.391 (1) Å with c/a = 2.002 The unit cell volume was calculated as U = 474.6 (2) Å3 and the X-ray density as Dx = 6.07 ± 0.003 gm cm−3. By comparing measured and theoretical intensity values, the sublattice distortion parameter x was estimated to be x = 0.227 (12).

Crystal structure analyses by the Rietveld method have shown that the framework structures of zeolites ZSM-5 and ZSM-8 are essentially identical. Therefore, it is difficult to distinguish the two phases especially when the template-free H forms are studied. In addition, some inconsistencies in publications on the two zeolites aggravate the correct interpretation of the powder diagrams. A powder pattern published for ZSM-8 which indicates significant differences between the lattice constants of ZSM-8 and ZSM-5 is shown to be incorrectly indexed. Correct reindexing gives lattice constants for ZSM-8 matching average ZSM-5 values. Peak splitting of a ZSM-8 reflection at 2θ≈23° (CuKα) has been used frequently to distinguish ZSM-8 from ZSM-5. However, it is also a common feature of ZSM-5 diagrams when the difference between a and b lattice constants is big enough to separate hkl and khl reflections within the instrumental resolution. Our data on two ZSM-8 samples indicate that cell dimensions of ZSM-8 do not deviate from average ZSM-5 values. It is suspected that effects in the decomposition of crystals upon calcination, and/or morphology and shape of twin individuals, and/or stacking faults account for different sorption properties of the two zeolites rather than differences in their average crystal structures.

Residual strains and microstresses are evaluated for both phase of a hot-pressed, fine-grained α-alumina reinforced with 25 wt% (29 vol%) single-crystal silicon carbide whiskers at temperatures from 25 to 1000 °C. The sample was maintained in a nonoxidizing environment while measurements of the interplaner spacing of alumina (146) and SiC (511 + 333) were made using X-ray diffraction methods. The residual strains were profiled at temperature increments of 250 °C from which the corresponding microstresses were calculated. Linear extrapolation of the SiC ε33 profile indicates that the strains are completely relaxed at a temperature of approximately 1470 °C. These residual stress relaxation results suggest that elevated temperature toughness and fracture strength of this composite may result from cooperative mechanisms.

Music, medicine, escape: Austria, Italy, America. As a very young man, Sigmund Weissmann, before he was 18, had seen the prosperous stability and direction of his youth disintegrate, had, through fortunate foresight and mature determination escaped potential disaster, and had found himself, essentially alone, in New York City. That was April 1939. Within 5 years, his early studies completed and military service over, his future had been established with crystallography, and even more particularly, that aspect of it which was related to the “pathology” of metals. He was to establish one of the first laboratories devoted to research of lattice defects and to lay the groundwork for what is now known as Materials Science. Contemporaneous with the operation of this laboratory and as an outgrowth of his own basic connection with the famous “Brooklyn Poly,” Weissmann included, among his manifold teaching, research, and consulting activities, the acceptance of a position as an editor of the Powder Diffraction File, the PDF. The PDF was then just large enough, just important enough and had just that suggestion of an important reach into the future to necessitate an equally important attention from a group of persons schooled and skilled in the most recent techniques of X-ray powder diffraction. Weissmann (metals), Ben Post (organics), of the Brooklyn Polytechnic Institute and J. V. Smith (minerals) (University of Chicago) were the first thus crystographically trained persons to oversee the PDF.

50-50 atomic percent lead telluride (Altaite), grown by the vapor transport method, was examined with a well aligned Rigaku horizontal beam diffractometer. PbTe is cubic (precise lattice parameter ao = 6.4591(5)Å) with an space group and a calculated density of 8.253 g/cm3. Fully indexed powder diffraction data are presented.

Barium titanyl oxalate tetrahydrate, Ba(TiO)(C2O4)2.4H2O, has been investigated by means of X-ray powder diffraction. Precise powder diffraction data were obtained by a conventional diffractometer with strictly monochromatic radiation. Unit cell dimensions were determined by an indexing program based on the variation of parameters by successive dichotomies. A monoclinic cell was found, a=14.044(2)Å, b=13.812(2)Å, c=13.382(2)Å, β=91.48(1); V=2594.9Å3, which is characterized by the figures of merit M20=46.5 and F30=107(0.0056, 50). The complete powder pattern was reviewed by means of the program NBS*AIDS83 and the 81 first lines were indexed. Structural imperfections were not detected from the diffraction line widths, which are comparable to the instrumental resolution.

A conventional semi-automated powder X-ray diffractometer that was previously equipped with a strip chart recorder for data acquisition has been interfaced to an HP 1000 minicomputer via an analog-to-digital converter. Data acquisition and analysis is now accomplished using CALS chromatographic software and two in-house-developed FORTRAN 77 computer programs. This has resulted in significant improvements in experimental repeatability and accuracy, decreased sample turn-around times, and rapid and facile analysis, manipulation, and comparison of crystallographic data.

Afghanite is a feldspathoid of the cancrinite-group: It is hexagonal, space group P63mc. The afghanite sample was found in the M. Somma-Vesuvio volcanic complex (Italy) and was previously described as davyne: Calculated cell parameters are a = 12.7997(4) Å, c = 21.4062(11) Å; the volume is 3037.2(2) Å3. The strongest lines are: 3.694(100), 3.647(56), 4.826(30), 2.678(25), 2.134(18), 3.999(12), 2.750(12), and 2.771(10). The new data provide quantitative measurement of intensities, an increased number of indexed peaks, and a different empirical formula with respect to the PDF 20-1086.

Recently, Dahan and co-workers (Dahan, 1991) suggested processing the XRD data by spreadsheet computer programs. Treated in this manner the XRD data became very flexible and made comparison with other data sets, as well as graphical presentation, much easier. In this note a simple FORTRAN 77 program for conversion of PC-APD data files into ASCII files suitable for import into spreadsheets is reported.

In our laboratory XRD data are collected on a Philips 1710 diffractometer operated by the PC-APD version 2.0 (PC-APD Software, 1989). Each experiment usually generates its files containing collected raw intensity data (.RD file), background data (.BK file) and file with peak positions and their intensities (.DI file). The XRD data can be further processed: after smoothing, data are stored in files with extension .SM (.SM file) and, after Kα2 stripping, into files with extension .A2 (.A2 file). All files are stored in the binary format.

The structure of pyrochlore type Y2Sn2O7 has been refined by Rietveld analysis from 1.4925 Å neutron powder diffraction data collected at 295 K and containing 46 independent reflections. The refinement figures of merit were Rp = 0.041, Rwp = 0.055, Rexp = 0.039, and RB = 0.006. The structure is a pyrochlore type, space group (S.G.) with a = 10.3723(1) Å, Dx = 6.21 g cm−3, and with the oxygen position parameter of 0.33694(5). The Sn atoms are in a nearly regular octahedral coordination whereas the Y has a distorted 8-fold coordination geometry. The anisotropic thermal parameters were also determined. The refined model has been used to calculate a set of d-I X-ray data for search/match analysis.

Possibilities and restrictions of least-square methods for mica cell refinement are briefly described. If diffractometric raw data are precise and accurate, and if geometrical errors are properly corrected, a cell refinement (determination of ao, bo, cO, β) can be carried out rapidly, but the reliability of obtained data has to be evaluated carefully.

A precise X-ray powder diffraction pattern of the orthorhombic form of InVO4, InVO4-III, was obtained using a Huber camera with CuKα1 radiation (λ=1.5406 Å) and Si as internal standard (a= 5.4308 Å). Refinements of indexed reflections led to the following parameters: a=5.7531(3)Å, b=8.5201(4)Å, c=6.5781(3)Å, space group Cmcm, Z =4, Dx=4.733 g/cm3, Dm=4.65 g/cm3. The Smith–Snyder figure-of-merit is F30=201.4 (0.004, 34).