The International Centre for Diffraction Data has an ongoing program to ensure the quality of data in the Powder Diffraction File (PDF) reflects current requirements of the powder diffraction community. Annual updates are made available, comprising of around 1800 new patterns and 200 replacement patterns, but current statistics indicate that only about 20% of users of the PDF take advantage of these updates. This paper reviews changes which have been inplemented in the editorial review process to continuously monitor and review pattern quality and gives examples of better data which have resulted from these changes.

Zr(MoO4)2 molybdate has been synthesized by solid state reaction. Single crystals were obtained by hydrothermal synthesis. Corrected crystal data are: monoclinic, a = 11.4309 (3), b = 7.9376 (2), c = 7.4619 (2) Å and β = 122.323 (2)°, V = 572.13 (6) /cm3 (5), Dx = 4.770 g/cm3. Powder diffraction data are reported.

The compound AlNbO4 has been studied by single crystal X-ray precession photographs and X-ray powder diffraction. Unit cell dimensions were calculated using a least squares analysis that refined to a Δ2θ° of no more than 0.03°. A monoclinic cell was found with space group C2/m, a = 12.1558(5)Å, b = 3.7345(2)Å, c = 6.4886(3)Å, and β = 107.613(4)°.

A program is presented that removes broadening from X-ray diffraction spectra. An instrumental spectrum can be used to describe empirically the broadening to be removed, or a Gaussian, Cauchy, or Pearson-VII distribution can be used to analytically describe it. In either case, singlet or doublet forms can be generated. The program returns the deconvoluted spectrum, the reconstructed spectrum, and a sum-of-squares difference between the original and reconstructed spectra. Deconvolution is accomplished using a combination of least-squares, background, and smoothing criteria that minimizes the effect of random counting errors.

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.

2,4,6-Trimercapto-s-triazine, trisodium salt (ideally, Na3S3C3N3·9H2O), also known as TMT-55, is a white powder that is used to precipitate heavy metals from contaminated waters. Chemical analyses confirmed the nominal composition. TMT-55 crystals are uniaxial negative with indices of refraction (25 °C) of nε=1.520 and nω=1.675. The structure was determined by single-crystal methods at 25 and −110 °C. A powder pattern was determined and compared to a simulated pattern based on the 25 °C structure data. Crystal data at 25 °C are: R3;Z=6; a=17.600(1) Å and c=9.720(2) Å; V=2607.5(5) Å3; Dx=1.55 g/cm3.

Potassium hydrogen fluoride KHF2 is tetragonal at room temperature: a=5.667(1) Å, c=6.795(1) Å, d=2.38, Z=4, space group I4/mcm (No. 140). It gives a polymorphic transition at 196 °C to a cubic form: a=6.435(1) Å, Z=4, space group Fm3m, melts at 239 °C, and then dissociates into gaseous HF and solid KF.

Four compounds in the hexafluoroniobates IV series MNbF6 (M=Ca, Mg, Cd, Zn) have been synthesized by solid-state reactions. CaNbF6, MgNbF6, and the “high temperature” form of CdNbF6 are isostructural with f.c. cubic NaSbF6 (space group Fm3m). ZnNbF6 and the room temperature form of CdNbF6 are isostructural with rhombohedral LiSbF6 (space group R3¯). Syntheses and powder diffraction data are reported.

The crystalline structure of new TlSr2PrCu207−x was obtained at room temperature (300 K) and low temperature (100 K) from X-ray powder diffraction with CuKα radiation using Rietveld analysis. TlSr2PrCu207−x has an isotypical structure with TlBa2CaCu207 (1212). At 300 K, crystal data: Tl0.864Sr2PrCu2O6.75, Mr=727.811, the tetragonal system, P4/mmm, a =3.85404(5) Å, c = 12.1046(2) Å, V=179.80 Å3, Z=1, Dx =6.7218 g cm−3, μ =1143.922 cm−1 (λ = 1.54051 Å), F(000)=317.0, the structure was refined with 28 parameters to Rwp=5.29%, Rp = 3.65% for 3551 step intensities and Rb=7.40%, Rf=639% for 155 peaks, “goodness of fit” 5=3.05. At 100 K, crystal data: Tl0.858Sr2PrCu2O6.61, Mr=724.345, the tetragonal system, P4/mmm, a =3.84872(6) Å, c = 12.0771(3) Å, V=178.89 Å3, Z=1, Dx=6.7235 g cm−3, μ=1146.939 cm−1 (λ= 1.54051 Å), F(000) = 315.4, the structure was refined with 26 parameters to Rwp=6.70%, Rp=5.11% for 2926 step intensities and Rb=7.83%, Rf=6.70% for 131 peaks, “goodness of fit” S = 1.75.