In the course of work, on the CaO-Nb205-Si02 System, a series of compositions on the Ca0-Nb2-05 binary join has been studied. There are indications of the existence of three calcium niobates. These compounds have been characterized by X-ray powder diffraction and optical data. Single crystal studies have given information concerning the crystallography of these materials.

Energy dispersive x-ray fluorescence is an established and versatile tool for measuring major and trace elements in virtually any kind of solid or liquid specimen. The usefulness of the method could he extended even further if the time of analysis for multicomponent samples could he reduced. In other words, we desire to analyze a wide range of elements with detection limits at least as good as obtained when the excitation conditions are optimized for a specific element or narrow range of elements. A major impediment to achieving this goal when analyzing bulk, low-Z materials is the scatter of source radiation into the detector by the specimen being analyzed. The adverse effects of the scattered radiation are its contribution to the background signal (i.e., “noise“) and its overwhelming contribution to the limited counting rate of the system electronics.

The crystal structure of sitagliptin dihydrogen phosphate monohydrate (sometimes referred to as sitagliptin phosphate monohydrate) has been solved and refined using synchrotron X-ray powder diffraction data, and optimized using density functional techniques. Sitagliptin dihydrogen phosphate monohydrate crystallizes in space group P212121 (#19) with a = 6.137 108(12), b = 9.304 018(14), c = 38.307 67(10) Å, V = 2187.359(8) Å3, and Z = 4. The sitagliptin cation folds so that the two planar portions are roughly parallel. The ammonium group of the sitagliptin cation, the phosphate anion, and the water molecule form a network of strong hydrogen bonds. The result is a two-dimensional network, parallel to the ab plane. Halfway between these hydrogen bond planes, there are planes of high fluorine density. The powder pattern is included in the Powder Diffraction File™ as entry 00-064-1500.

New powder and crystallographic data for gorceixite, a mineral of the crandallite subgroup of the alunite group, are reported and compared with current Powder Data File (PDF) patterns and with calculated patterns. Both d-spacings and intensities have been evaluated, and the results indicate a significant improvement over existing patterns. Indexing of the reflections is given for the true monoclinic symmetry, Cm (8), the pseudorhombohedral symmetry, (166) (to compare with structurally analogous minerals), and the pseudocubic symmetry, Fm3m (225). Because of the strong pseudosymmetry, the overall figure of merit is lower than would be the case for indexing in one of the pseudospace groups.

An experimental X-ray powder diffraction pattern was produced and analyzed for alpha-polymorphic tegafur, also called Ftorafur (an antineoplastic agent). The indexed data matched the powder patterns in the ICDD PDF-4/Organics database calculated from the reported single-crystal X-ray diffraction data in the Cambridge Structural Database. Alpha tegafur has a triclinic crystal system, with reduced cell parameters of a=16.720(6) Å, b=9.021(5) Å, c=5.995(3) Å, α=93.66(4)°, β=93.15(8)°, γ=100.14(4)°. There are four formula units contained in one unit cell. The cell volume and space group were determined to be 886.27 Å3 and P-1, respectively.

Two new VAX/VMS computer programs are presented for accessing and searching the Powder Diffraction File (PDF) (1989) of the JCPDS-International Centre for Diffraction Data (ICDD). The programs use binary mapped index files which affords rapid searches of the database. Program LOGIC permits entries in the database to be selected by chemistry, peak position or name constraints. The selected entries may be displayed, printed or graphed. The program can display or print entries from the full PDF-2 (1989) database, if on-line. Program SEARCH searches for patterns in the database which match an unknown set of peaks; the program may be optimized for a wide variety of applications including identification of component phases in mixtures. Commands may be entered to the programs in two modes. In the “novice-friendly” mode, users must answer questions to select options. However, experienced users may opt to use a concise one-line command syntax. The modes may be mixed.

The synthesis and X-ray powder diffraction data for the organometallic [Rh2(bim)2(cod)2]Cl2∙2H2O species are reported. Its crystal and molecular structures were determined by simulated annealing and full-profile Rietveld refinement methods. [Rh2(bim)2(cod)2]Cl2∙2H2O was found to crystallize in the orthorhombic Cmca space group. The lattice parameters were determined to be a=21.3574(6), b=10.7764(3), c=14.2795(4) Å, V=3286.5(2) Å3, for Z=4. The crystal structure was found to contain dimeric [Rh2(bim)2(cod)2]2+ cations, in which the bim ligands bridge Rh(cod) fragments with an intermetallic separation of ca. 8.90 Å. The crystal structure is completed by chloride ions and hydrogen-bonded water molecules, situated in the small cavities of the large cation substructure. The conformation of the bim ligand, lying on a crystallographic mirror plane, is rigorously Cs.

Fe–N thin films were deposited on glass substrates by dc magnetron sputtering under various Ar∕N2 discharge conditions. Crystal structures and elemental compositions of the films were characterized by X-ray diffraction and X-ray photoelectron spectroscopy. Magnetic properties of the films were measured using a superconducting quantum interference device magnetometer. Films deposited at different N2∕(Ar+N2) flow ratios were found to have different crystal structures and different nitrogen contents. When the flow ratios were 60%, 50%, and 30%, a nonmagnetic single-phase FeN was formed in the films. At the flow ratio of 10%, two crystal phases of γ′-Fe4N and ε-Fe3N were detected. When the flow ratio reduced to 5%, a mixture of α-Fe, ε-Fe3N, FeN0.056, and α″-Fe16N2 phases was obtained. The value of saturation magnetization for the mixture was found to be larger than that of pure Fe.

This paper further confirms that the direct measurement of diffraction angles at different temperatures by using the X-ray diffractometer is better than measurement of the lattice parameters for the rapid and accurate determination of the linear thermal expansion of silicon. High purity silicon has the linear expansion coefficient, α= (2.45±0.05) × 10−6/°C at room temperature. This value does not change for doped P-type and N-type silicon.

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.

X-ray diffraction techniques have been applied to study the crystallization of poly(ethylene-2,6-naphthalate), PEN. Uniaxial and biaxial orientation of amorphous cast PEN films resulted in stress-induced crystallization of the triclinic α-PEN polymorph. Annealing of the amorphous PEN samples in the range of 160–240 °C produced thermally induced crystallization of α-PEN. Slow cooling of amorphous PEN from the melt state generated α-PEN as well as the triclinic β-PEN polymorph.

Several hitherto unknown hydrates of magnesium selenate have been formed by quenching aqueous solutions of MgSeO4 in liquid nitrogen. MgSeO4·11H2O is apparently isostructural with the mineral meridianiite (MgSO4·11H2O), being triclinic, $P{\rm \bar 1}$, Z = 2, with unit-cell parameters a = 6.779 00(8) Å, b = 6.965 16(9) Å, c = 17.4934(2) Å, α = 87.713(1)°, β = 89.222(1)°, γ = 63.121(1)°, and V = 736.15(1) Å3 at −25 °C. MgSeO4·9H2O represents a new hydration state in the MgSeO4–H2O system; it is monoclinic, space-group P21/c, Z = 4, with unit-cell parameters a = 7.270 24(6) Å, b = 10.510 94(9) Å, c = 17.4030(2) Å, β = 109.447(1)°, and V = 1254.02(1) Å3 at −22 °C. The heavy-atom structure of MgSeO4·9H2O has been determined by direct-space methods from X-ray powder diffraction data and consists of isolated Mg(H2O)62+ octahedra and SeO42− tetrahedra linked by hydrogen bonds. The remaining three water molecules occupy the space between the polyhedral ions, contributing to the H-bonded network, which comprises 4-, 5-, and 6-membered rings. A third phase has been observed to crystallise prior to the 11-hydrate upon warming of liquid-nitrogen-quenched glass, but this transforms rapidly to the meridianiite-structured 11-hydrate and the identity of this phase is unclear.

Powder X-ray diffraction patterns for three forms of MIL-53(Al), a metal organic framework (MOF) compound with breathing characteristics, were investigated using the Rietveld refinement method. These three samples are referred to as the MIL-53(Al)as-syn (the as synthesized sample), orthorhombic, Pnma, a = 17.064(2) Å, b = 6.6069(9) Å, c = 12.1636(13) Å, V = 1371.3(2) Å3, Z = 4), MIL-53(Al)LT-H (low-temperature hydrated phase, monoclinic P21/c, a = 19.4993(8) Å, b = 15.2347(6) Å, c = 6.5687(3) Å, β = 104.219(4) °, V = 1891.55(10) Å3, Z = 8), and MIL-53(Al)HT-D (high-temperature dehydrated phase, Imma, a = 6.6324(5) Å, b = 16.736(2) Å, c = 12.840(2), V = 1425.2(2) Å3, Z = 4). The crystal structures of the “as-syn” sample and the HT-D sample are confirmed to be the commonly adopted ones. However, the structure of the MIL-53(Al)LT-H phase is confirmed to be monoclinic with a space group of P21/c instead of the commonly accepted space group Cc, resulting in a cell volume double in size. The structure has two slightly different types of channel. The pore volumes and pore surface area were estimated to be 0.11766 (8) cm3/g and 1461.3(10) m2/g for MIL-53(Al)HT-D (high-temperature dehydrated phase), and 0.08628 (5) cm3/g and 1401.6 (10) m2/g for MIL-53(Al)as-syn phases, respectively. The powder patterns for the MIL-53(Al)as-syn and MIL-53(Al)HT-D phases are reported in this paper.

Divalent metal ions are crucial as cofactors for a variety of intracellular enzymatic activities. Mg2+, as an example, mediates binding of deoxyribonucleoside 5′-triphosphates followed by their hydrolysis in the active site of DNA polymerase. It is difficult to study the binding of Mg2+ to an active site because Mg2+ is spectroscopically silent and Mg2+ binds with low affinity to the active site of an enzyme. Therefore, we substituted Mg2+ with Mn2+:Mn2+ that is not only visible spectroscopically but also provides full activity of the DNA polymerase of bacteriophage T7. In order to demonstrate that the majority of Mn2+ is bound to the enzyme, we have applied site-directed titration analysis of T7 DNA polymerase using X-ray near edge spectroscopy. Here we show how X-ray near edge spectroscopy can be used to distinguish between signal originating from Mn2+ that is free in solution and Mn2+ bound to the active site of T7 DNA polymerase. This method can be applied to other enzymes that use divalent metal ions as a cofactor.

This paper introduces the historical development of the symmetries for describing magnetic structures culminating in the derivation of the black and white and coloured space groups. Beginning from the Langevin model of the Curie law, it aims to show the challenges that magnetic ordering presented and how different symmetry frameworks were developed to meet them. As well as explaining core ideas, later papers will show how the different schemes are connected. With these goals in mind, the maths related is kept to the minimum required for clarity. Those wishing to learn more details are invited to engage with the references. As well as looking back and reviewing the development of magnetic symmetry over time, particular attention is spent on explaining where the concept of time-reversal has been applied. That time-reversal has different meaning in classical and quantum mechanical situations, has created confusions which continue to propagate.

Lead poisoning is a preventable condition caused by exposure to environmental sources such as lead-containing dust or lead-painted consumer products. The history of lead poisoning prevention has been defined to some extent by the quality of the analytical methods available for lead measurements whether in environmental samples or biological tissues and fluids. The quality of blood lead methods has improved so greatly over the last three decades that we now know far more about the adverse health effects from low-level exposures. Recent evidence suggests that effects such as deficit in IQ occur below the current (periodically revised) U.S. CDC threshold of 10 μg/dL, such that no safe threshold appears to exist for children. Improvements in analytical techniques have also had an impact on the environmental measurement quality, yet many environmental thresholds have remained unchanged for decades. In light of our current understanding of the adverse health effects at low levels of exposure, new thresholds for lead in children’s products have been introduced by the U.S. CPSC. The adequacy of current analytical techniques to detect lead accurately at the new, lower thresholds is questionable. XRF offers the advantage of being rapid and nondestructive compared to techniques such as AAS that require extensive sample preparation. However, the accuracy of handheld XRF determinations of lead in painted toys is generally limited. A brief comparative study on the performance of several analytical techniques for the determination of lead in toys is presented at the end of this paper.

Crystal structures of Li(Ta0.89Ti0.11)O2.945 and (Li0.977Eu0.023)(Ta0.89Ti0.11)O2.968 were investigated by laboratory X-ray powder diffraction. Both title compounds were trigonal with space group R3c and Z = 6. The hexagonal unit-cell dimensions were a = 0.514 82 9(2) nm, c = 1.377 61 2(4) nm, and V = 0.316 21 6(2) nm3 for the former compound and a = 0.517 71 2(2) nm, c = 1.373 50 0(6) nm, and V = 0.318 81 2(3) nm3 for the latter. The initial structural models, being isostructural with LiTaO3, were refined by the Rietveld method. The maximum-entropy method-based pattern fitting (MPF) method was subsequently used to confirm the validity of the structural models, in which conventional structure bias caused by assuming intensity partitioning was minimized. Atomic arrangements of the final structural models were in excellent agreement with the three-dimensional electron-density distributions determined by MPF.

The scanning speed of powder diffractometers can be increased by about two orders of magnitude by replacing the normal detection system (receiving slit/scintillation counter) by a linear position sensitive detector (PSD) which collects diffracted x-rays of a larger part of the diffractometer measuring arc simultaneously. The velocity increase is proportional to the section of the arc 29 in which the diffracted x-rays are detected. With respect to the Bragg-Brentano focussing geometry, a range of several degrees (typically 5°) can be tolerated without affecting the resolution remarkably. Diffractograms over extended angular regions of 2θ are received by slewing the PSD continuously along the arc while the diffracted x-rays are accumulated with their accurate 2θ angle address on a digital base.

The method has been named the continuous position sensitive detection technique (CPSD). With this technique, diffraction patterns with similar quality (resolution, linearity, peak/background ratio) as conventional, scintillation counter recorded diagrams can be received at slewing rates of several hundred degrees per minute. Additionally, the CPSD technique augments the number of crystallites contributing to the diffraction intensity by the same amount, thus producing much better crystallite statistics for quantitative measurements.

Several compositions of the solid solutions (CaxSr1−x)CuO2 and (CaxSr1−x)2CuO3, both of which are found as minor phases in the high-temperature superconductors, were prepared by solid-state reaction. X-ray powder-diffraction patterns for three compositions of (CaxSr1−x)CuO2 and two for (CaxSr1−x)2CuO3 are presented.

An expanded X-ray quantitative phase analysis method is presented. It is an extension of the method without standards. In order to get the method applied more extensively, there is a discussion at the end of this paper of the suitability of samples.