Crystal structure and structural disorder of Ba3MgSi2O8 were reinvestigated by laboratory X-ray powder diffraction. The title compound was found to be trigonal with space group P3m1, Z=1, and unit-cell dimensions a=0.561 453(4) nm, c=0.727 629(4) nm, and V=0.198 641(2) nm3. The initial structural model used for structure refinement was taken from that of glaserite (K3NaS2O8) and modified by a split-atom model. In the split-atom model, one of the two types of Ba sites and that of SiO4 tetrahedra were, respectively, positionally and orientationally disordered. The new crystal structure and structural disorder were refined by the Rietveld method. The maximum-entropy-method-based pattern fitting (MPF) method was used to confirm the validity of the split-atom model, in which conventional structure bias caused by assuming intensity partitioning was minimized. The final reliability indices calculated from MPF were Rwp=6.52%, S=1.36, Rp=4.84%, RB=0.97%, and RF=0.52%. Details of the disorder structure of Ba3MgSi2O8 are shown in the three-dimensional and two-dimensional electron-density distribution maps determined by MPF.

θ-KAlF4 is a new nanosized potassium tetrafluoroaluminate metastable polymorph (13×18×55 nm3). The crystal structure is solved ab initio from X-ray powder diffraction data in direct space [orthorhombic unit cell with a=8.3242(3) Å, b=7.2502(3) Å, c=11.8875(4) Å, V=717.44(5) Å3, Z=8, and space group Pnma]. This new structure type, unique in the whole AIMIIIF4 family, is related to the fluorite structure and consists of AlF6 octahedra linked via a common edge forming a bioctahedral motif which is trans-connected through the corner-shared fluorine, resulting in the formation of infinite ladderlike double file of octahedra ([Al2F8]2−)n running along the b axis.

The solid-state phase transformation from α- to β-copper phthalocyanine, using isothermal data obtained at T=250 °C and nonisothermal data obtained in the temperature range of 30 °C≤T≤330 °C with a constant heating rate of 1.67 °/min, was investigated by sequential and parametric full quantitative Rietveld analyses. Results obtained in this study show that the parametric Rietveld refinement technique is most suitable and applicable for kinetic studies of isothermal powder diffraction data. On the other hand, the sequential Rietveld refinement technique can give reliable results for the kinetic analysis of nonisothermal data. The main advantages of the parametric Rietveld refinement over the sequential Rietveld refinement are increased robustness against outliers, low weight fractions, and noisy data and an increase in computational speed.

Sr0.5Zr2(AsO4)3 arsenate was prepared and structurally characterized by powder X-ray diffraction and by Raman and infrared spectroscopies. Its structure, which belongs to the Nasicon-type family, was refined by the Rietveld method in the R-3 space group, from X-ray powder diffraction data. The hexagonal unit-cell parameters were determined to be ah=8.965(2) Å, ch=23.955(6) Å, V=1667.43(6) Å3, and Z=6. The structure is formed by an ionic three-dimensional network of AsO4 tetrahedra and ZrO6 octahedra linked by corners with Sr2+ ions occupying half of the M1 sites in an ordered manner. Raman and infrared spectra were recorded and assignments of the stretching and bending vibrations of the AsO43− tetrahedra were made. The number of the peaks observed is in good agreement with that predicted by the factor-group analysis of the R-3 space group.

Four sol-gel TiO2 powders have been prepared from titanium tetraisopropoxide. The calcined powders are then characterized by X-ray diffraction. Cell parameters are extracted using two Rietveld refinement programs (FULLPROF and MAUD) leading to close values and indicating a contraction of the a (or b) cell parameter and an expansion of the c cell parameter of the anatase phase with temperature. Crystallite size and microstrain are highly dependent not only on the sol synthesis but also on the diffraction line profile analysis (LPA) models (i.e., Williamson-Hall, Thomson-Cox-Hastings, Dehlez et al., and log-normal size distribution) employed. Discrepancies are then observed for the phase transformation critical size, the activation energy of grain growth, and the microstrain stored potential energy according to the LPA approach used to calculate the microstructural parameters.

A synthetic analogue, Ca(Ti0.6Al0.2Sb0.2)OSiO4, of antimony-bearing titanite of a composition similar to that found at St. Marcel-Praborna (Italy) was synthesized using ceramic methods and the crystal structure was refined using the Rietveld method. Unit-cell dimensions (in Å) are a=7.0184(1), b=8.7097(2), c=6.5586(1), and β=113.700(1)°. The substitution of 40% Ti by (Al+Sb) in octahedra causes a loss of long-range coherency of the off-centered Ti atoms. The space group of Sb-bearing titanite is A2/a, like other cases of M3+-M5+-doped titanites. This study confirms that titanite with up to 0.2 Sb atom per f.u. can exist and that the substitution scheme is 2Ti4+↔Al3++Sb5+.

The modified Williamson–Hall and Warren–Averbach methods were used successfully for analyzing experimentally observed anisotropic X-ray diffraction line broadening and for determining reliable values of crystallite size and dislocation density in cerium oxide. The modified Williamson–Hall plot gives 22.3(2) nm for volume-weighted crystallite size, while the modified Warren–Averbach produces 18.0(2) nm for area-weighted grain size. The dislocation density and effective outer cut-off radius of dislocations obtained from the modified Warren–Averbach method are 1.8(3)×1015 m−2 and 15.5(1) nm, respectively.

NaCl1−xBrxO3 single crystals were prepared by unidirectional crystallization. The influences of the composition on structure, quality, and optical properties of NaCl1−xBrxO3 crystals were investigated. X-ray powder diffraction analysis revealed that the diffraction patterns for the NaCl1−xBrxO3 crystals have almost the same set of peaks as those of NaClO3 and NaBrO3, except that an extra very weak forbidden (100) diffraction peak was detected at about 13.3° 2θ for crystals grown from solutions of BrO3−∼15–70 at. % (i.e., x=0.15–0.70). These crystals can, therefore, be considered to have a distorted cubic structure closely related to the cubic structures of NaClO3 (x=0) and NaBrO3 (x=1). Our study also found that good-quality crystals can only be obtained in two doping ranges (x>0.75 or x<0.10). Outside these two ranges, the crystals tended to crack and even became opaque. Lattice distortions in the crystals were the probable cause as revealed by X-ray powder diffraction patterns. The optical activity of NaCl1−xBrxO3 crystals measured by a laser was found to decrease from 2.89 to 2.01°/mm with increasing value of x from 0 to 0.02. Stimulated Raman scattering of NaBr0.90Cl0.10O3 crystals was measured using a 0.532-μm ps laser as a pump source and four anti-Stokes lines plus six Stokes lines were observed. The fourth anti-Stokes emission was found to be at 454.5 nm and the sixth Stokes emission at 713.6 nm. Its Raman gain coefficient was determined to be 18.4 cm/Gw.

The Rietveld method is increasingly used for amorphous portion determination. This article describes the quantification of amorphous portions using an internal standard in a formal mathematical way. From a set of basic assumptions and postulations, equations for the amorphous portion quantification, the optimum amount of internal standard, and the slope of the amorphous portion calculation formula were derived. With this tool set, the influence of the method principle on the analytical uncertainty is discussed. It is shown that the amount of internal standard has a strong influence on the precision of the amorphous portion determination. A poor choice can make the determination impossible, while a clever choice can enhance the precision compared to the precision of the Rietveld refinement.

A new single-phase copper chromate compound was successfully synthesized by a hydrothermal method and characterized by XRD, SEM, TGA, and XRF analysis. The experimental XRD pattern was analyzed by automatic indexing and the compound was found to be monoclinic with space group P21/a and unit-cell parameters of a=10.1829(11) Å, b=4.9516(6) Å, c=7.2899(7) Å, and β=103.64(1)°. The chemical formula of the copper chromate compound determined by XRF and TGA was determined to be (NH4)1.5Cu2Cr2O8(OH)1.5⋅H2O. XRD results also showed that the synthesized compound decomposed into CuCr2O4 and CuO after being calcined at 600 °C.

Compound HoCo0.67Ga1.33 was synthesized and studied by means of X-ray powder diffraction technique. HoCo0.67Ga1.33 was found to have the orthorhombic CeCu2 structure (space group Imma) with a=4.3479(2) Å, b=7.0351(3) Å, c=7.4876(3) Å, Z=4, and Dcalc=8.62 g/cm3. The crystal structure of HoCo0.67Ga1.33 was also refined by the Rietveld method. Ho atoms were found to occupy the 4e positions and mixed Co/Ga atoms to share the 8h positions of the space group Imma (No. 74).

The room temperature powder pattern of lapatinib ditosylate monohydrate (active ingredient in Tykerb used to treat refractory breast cancer) was indexed and the cell from the single crystal X-ray diffraction structure was refined using the experimental capillary data. Unit-cell parameters for the orthorhombic compound with space group Pbca refined from powder diffraction data are a=9.6850±0.0009 Å, b=29.364±0.003 Å, and c=30.733±0.003 Å, α=β=γ=90°, z=8, V=8740.1 Å3. Values of 2θ, d, I, and Miller indices are reported.

The results from a third structure determination by powder diffractometry (SDPD) round robin are discussed. From the 175 potential participants having downloaded the powder data, nine sent a total of 12 solutions (8 and 4 for samples 1 and 2, respectively, a tetrahydrated calcium tartrate and a lanthanum tungstate). Participants used seven different computer programs for structure solution (ESPOIR, EXPO, FOX, PSSP, SHELXS, SUPERFLIP, and TOPAS), applying Patterson, direct methods, direct space methods, and charge flipping approach. It is concluded that solving a structure from powder data remains a challenge, at least one order of magnitude more difficult than solving a problem with similar complexity from single-crystal data. Nevertheless, a few more steps in the direction of increasing the SDPD rate of success were accomplished since the two previous round robins: this time, not only the computer program developers were successful but also some users. No result was obtained from crystal structure prediction experts.

An additional statistical calibration for the Bruker D8 Discover microdiffractometer is necessary to obtain accurate reproducible 2θ data for cell-refinement work. This new approach uses a graphical mapping method of the 2θ error versus the location of a selected diffraction peak on the detector surface to describe the separate roles of different calibration procedures (rebiasing, flood field, and spatial corrections) and parameters (sample-to-detector distance, x-y center coordinate) in minimizing the error. Optimized parameters are used to obtain the lowest achievable Δ2θ with this setup. Intensity error relative to the position of the diffracted line on the detector was found to be consistent at up to 20% and could not be reduced using any of the investigated techniques and parameters.