The systems PbO–Bi2O3–P2O5/As2O5/V2O5 have been studied with respect to their compounds and solid solutions. A number of new compounds, particularly with high-Bi contents were found. Most of them are structurally closely related to the CaF2 and δ-Bi2O3 structures. Several binary and ternary solid solutions with P/As/V substitutions were investigated.

The structure of the oxyphosphate Ni0.50TiO(PO4) has been determined ab initio from conventional X-ray powder diffraction data by the “heavy atom” method. The cell is monoclinic (space group P21/c, Z=4) with a=7.3830(5) Å, b=7.3226(5) Å, c=7.3444(5) Å, and β=120.233(6)°. Refinement of 46 parameters by the Rietveld method, using 645 reflexions, leads to cRwp=0.152, cRp=0.120, and RB=0.043. The structure of Ni0.50TiO(PO4) can be described as a TiOPO4 framework constituted by chains of tilted corner-sharing TiO6 octahedra running parallel to the c axis, crosslinked by phosphate tetrahedra and in which one-half of octahedral cavities created are occupied by Ni atoms. Ti atoms are displaced from the center of octahedra units in alternating long (2.231) and short (1.703 Å) Ti–O bonds along chains.

Error quantities, defined earlier to estimate the accuracy of texture measurement, are used to define a probability criterion for correct indexing of powder diffraction diagrams. The criterion is based on the compatibility of pole density distribution functions of different (hkl) depending on the directions {θ,γ}(hkl) of the reciprocal lattice vectors r*(hkl). The criterion was applied to permutation of the indices and variation of the angles {θ,γ}(hkl) in the vicinity of the correct values. In fortunate case, these angles can be determined within a few degrees by minimizing the error quantities. The method works very well with strong textures but it is still applicable if only weak textures can be achieved. The method was tested with different crystal symmetries including cubic, hexagonal, orthorhombic, and monoclinic. It is concluded that the criterion can be successfully applied to all crystal symmetries. If a measuring technique based on a position sensitive detector is used, even multifold peak superpositions in tilted sample orientations can be resolved. The method can also be applied if some (hkl) cannot be separated experimentally.

X-ray powder diffraction data for the compound 2-nitro-l-phenyl-prop-l-ene, C9H9NO2 are reported. The crystals are orthorhombic and the space group is Pbca[61], with a = 7.576(2), b = 19.452(5), c = 11.269(4)Å, Z = 8 Dx = 1.305, Dm = 1.300(2) g/cm3.

The following sixteen reference patterns of boride, silicide, nitride and oxide ceramics represent the second group of reference patterns measured at the National Bureau of Standards under the project “High Quality Reference Patterns and Total Digital Powder Patterns of Technologically Important Ceramic Phases”. Included in the sixteen reference patterns are data for two high Tc superconducting oxide phases (CuSr0.2La1.8O4 and Ba2Cu3YO7) plus one related phase (BaCuY2O5). In addition to these new phases, five other patterns represent phases previously not contained in the PDF and eight represent major corrections to data in the file. The general methods of producing these X-ray powder diffraction reference patterns are described in this journal, Vol. 1, No. 1, pg. 40 (1986).

μPDSM, a powder diffraction search/match system, is derived from the original interactive time-sharing system written for the NIH/EPA Chemical Information System. Transformed and essentially rewritten, it still searches the entire JCPDS database, but on an inexpensive IBM PC microcomputer. In the transition from mainframe to micro, μPDSM has lost none of its speed or performance. Indeed, the basic discriminating power of the search/match algorithms had to be improved, since the Powder Diffraction File is some 50% larger than it was when The CIS version was in operation. While μPDSM will solve typical problems on a “push-button” mode, it provides an environment that promotes optimization of search parameters by the diffractionist, and provides all of the subfile and chemistry functions associated with larger systems.

The X-ray powder diffraction patterns for three bulk Zn1−xMgxSe crystals are reported. The data were obtained with the help of an automated Bragg–Brentano diffractometer using Ni-filtered Cu Kα radiation. One of the samples is of the sphalerite structure type, and it has the magnesium content slightly below the sphalerite–wurtzite phase transition. The two remaining ones are of the wurtzite type with low and high magnesium content. The lattice constant for the sphalerite Zn0.86Mg0.14Se is a0=5.7011(1) Å. For the wurtzite alloys the lattice constants are a0=4.0540(1) Å, c0=6.6270(2) Å (for Zn0.72Mg0.28Se), a0=4.1195(1) Å, c0=6.6941(2) Å (for Zn0.37Mg0.63Se).

Indexed X-ray powder diffraction data are reported for the homologous compound (ZnO)5(In1−xYx)2O3. The structures of (ZnO)5In2O3 and of (ZnO)5(In1−xYx)2O3 were refined by the Rietveld technique on the basis of the space group R3¯m. Refined unit cell dimensions are a=3.3285(1) Å, c=58.127(2) Å, V=557.71(3) Å3, Dx=6.11 g/cm3, Rwp=10.52, RB=8.56 for (ZnO)5In2O3, and a=3.3505(1) Å, c=57.863(1) Å, V=562.53(2) Å3, Dx=5.97 g/cm3, Rwp=9.05, RB=6.94 for (ZnO)5(In0.8Y0.2)2O3. The structure of (ZnO)5In2O3 was shown to be isostructural with (ZnO)5LuFeO3. Y3+ ions were determined to be arranged at the 3a-metal sites substituting for In3+ ions.