In an attempt to fill a gap between fully automatic search/match programs and purely manual methods based on paper products, a relational database plug-in has been developed that functions as a PC-based Search/Index program for extracting information from PDF-4 powder diffraction databases. The plug-in provides an adjustable search window and match window to account for experimental errors. Both Hanawalt and Fink search methods are incorporated. In this paper, we report search-indexing results obtained with the new PDF-4 plug-in applied to a new relational database, the PDF-4/Organics 2003. This database has 24 385 experimental entries and 122 816 calculated patterns derived from the Cambridge Crystallographic Database. We introduce a goodness of match (GOM) parameter to describe the relative agreement between the experimental input data and selected reference patterns from the PDF-4/Organics 2003. The relevance of the GOM is illustrated in several example problems. Multiphase samples can be treated on a phase-by-phase basis.

The compound ammonium D-gluconate (C6H11O7−NH4+) has been studied by X-ray powder diffraction. The powder diffraction pattern and data obtained at room temperature are presented (cell data and powder data summary).

All known occurrences of nickelphosphide (Ni,Fe)3P—a mineral encountered mainly in meteoritic irons—represent relatively small grains, which prevents acquiring powder data of a reasonable quality. Synthetic analogues of this mineral, corresponding chemically to that found in the meteorite Vicenice, have been synthesized. Powder data collected using a standard laboratory diffractometer in the Bragg–Brentano geometry are presented. The space group of nickelphosphide is identical to that of schreibersite (Fe,Ni,Co)3P and synthetic Ni3P—I4. The unit-cell dimensions refined from the powder data are a=9.0168(1) Å, c=4.4501(1) Å, and V=361.80(1) Å3, with Z=8.

Solid lipid nanoparticles (SLNs) were characterized by differential scanning calorimetry (DSC) and powder diffraction. The DSC thermograms showed a slight reduction in the melting point of lipid matrix and a broadening of its melting peak, indicating an increased number of lattice defects in SLNs. X-ray powder diffraction data also revealed a slightly broader reflection for SLNs and the presence of X-ray peaks of the all-trans retinoic acid (RA) crystals outside of the lipid matrix of SLNs without stearylamine (STE). These data suggest the presence of an extensive association of ion pairing components (RA and STE), and indicate that the utilization of some specific types of compounds containing amine groups is an interesting approach to improve the encapsulation efficiency of RA in SLNs. The formation of the ion pairing is an interesting alternative for RA encapsulation in SLNs, improving the benefits obtained by the drug incorporation in lipid matrix (increased stability, controlled release, and targeting effect), which are important for the topical treatment of acne.

Two novel copper and iron chelates have been studied by powder diffraction. The cell parameters for triclinic (space group P 1 (2)) C25H21CuN3SO4 are a=9.636(2) Å; b=11.014(1) Å; c=11.233(3) Å; α=83.55(2); β=82.45(6); γ=76.36(2); Z=2; Dx=1.456 g cm−3. The monoclinic cell parameters (space group P 21/c (14)) for C40H30Cl4Fe2N8S2 are a=11.464(8) Å; b=17.462(1) Å; c=20.550(6) Å; β=103.534(1); Z=2; Dx=1.356 g cm−3.

Mixed solvent of ethanol and water using FeSO4⋅7H2O and (NH2)2CS as precursors with polyvinylpyrrolidone as surfactant was used to synthesize cubic FeS2 (pyrite) crystals. Crystalline phase and surface morphologies of the crystals were characterized by X-ray diffraction and scanning electron microscopy, respectively. Volume ratio of solvent, reaction temperature, reaction time, and sulfur source were found to be the key parameters for the formation of pure pyrite crystals. Optimal micron-size pyrite crystals were successfully grown from a mixed solvent of ethanol and water with a volume ratio of 3:2, heated to a reaction temperature of 180 °C, and maintained for 36 h with thiourea as the sulfur source.

Nanocrystals of Zn1−xMxO (M=Mn, Co, or Ni) were grown using proteic sol-gel process, and the crystalline phases were identified by X-ray diffraction and Rietveld refinement. The nanocrystals have hexagonal wurtzite structure, with space group P63mc. The insertion of Mn2+ in the place of Zn2+ provoked an increase in the size of the nanocrystals, and the insertion of Co2+ or Ni2+ caused a reduction in the sizes of the nanocrystals, as compared to pure ZnO. This occurred because these three transition metals have very different ionic radii (Co2+=0.58 A˚, Mn2+=0.66 A˚, Ni2+=0.55 A˚, and Zn2+=0.60 A˚).

Results of crystal structure refinements and phase quantification for samples of Co-doped lanthanum chromites with nominal composition LaCr1−xCoxO3, for x=0.00, 0.10, 0.20, and 0.30, prepared by combustion synthesis are presented. The resulting powders were characterized by scanning electron microscopy and X-ray diffraction (XRD). The XRD patterns were obtained with Cu Kα radiation for non-doped lanthanum chromite sample and additionally with Cr Kα radiation for Co-doped lanthanum chromites samples, in order to enhance the signal from scattering. Rietveld analysis of XRD data showed that the studied samples presented the lanthanum chromite with an orthorhombic structure (Pnma), except for the composition with x=0.30, in which the space group was found to be R3c.

The structure of [Al2(pydc)2(μ2-OH)2(H2O)2]n(pydc = 2,5-pyridinedicarboxylate) was successfully determined from powder X-ray diffraction data. The compound crystallizes in the triclinic system (space group P -1) with a = 6.7813(1) Å, b = 7.4944(1) Å, c = 8.5013(1) Å, α = 95.256(1)°, β = 102.478(1)°, γ = 108.979(1)°. The structure consists of aluminum ions coordinating N and O in distorted octahedra, sharing an edge through two hydroxide ions. These dinuclear complexes are connected by pydc ions, which at one end coordinate by nitrogen and oxygen and only by oxygen at the other end. The pydc orientation is reversed in the neighboring pydc, forming double stranded chains interconnected by the aluminum dinuclear complexes in a ladder-like arrangement along [001].

Crystal structure of compositionally homogeneous, nanocrystalline ZrO2–CeO2 solutions was investigated by X-ray powder diffraction as a function of temperature for compositions between 50 and 65 mol % CeO2. ZrO2-50 and 60 mol % CeO2 solid solutions, which exhibit the t′-form of the tetragonal phase at room temperature, transform into the cubic phase in two steps: t′-to-t″ followed by t″-to-cubic. But the ZrO2-65 mol % CeO2, which exhibits the t″-form, transforms directly to the cubic phase. The results suggest that t′-to-t″ transition is of first order, but t″-to-cubic seems to be of second order.

The fuzzy frontiers between structure determination by powder diffractometry and crystal structure prediction are discussed. The application of a search-match program combined with a database of more than 60 000 predicted powder diffraction patterns is demonstrated. Immediate structure solution (before indexing) is shown to be possible by this method if the discrepancies between the predicted crystal structure cell parameters and the actual ones are <1%. Incomplete chemistry of the hypothetical models (missing interstitial cations, water molecules, etc.) is not necessarily a barrier to a successful identification (in spite of inducing large intensity errors), provided the search-match is made with chemical restrictions on the elements present in both the virtual and experimental compounds.

The structure of the oxyphosphate Li0.50Ni0.25TiO(PO4) has been determined from conventional X-ray and neutron powder diffraction data. The parameters of the monoclinic cell (space group P21/c, Z=4), obtained from X-ray results, are: a=6.3954(6) Å, b=7.2599(6) Å, c=7.3700(5) Å, and β=90.266(6)°; those resulting from neutron study are: a=6.3906(7) Å, b=7.2568(7) Å, c=7.3673(9) Å, and β=90.234(7)°. Refinement by the Rietveld method using whole profile, leads to satisfactory reliability factors: cRwp=0.128, cRp=0.100, and RB=0.038 for X-ray and cRwp=0.110, cRp=0.120, and RB=0.060 for neutrons. The structure of Li0.50Ni0.25TiO(PO4) can be described as a TiOPO4 framework constituted by chains of tilted corner-sharing TiO6 octahedra running parallel to the c axis and cross linked by phosphate tetrahedra. In this framework, there are octahedral cavities occupied by Li and Ni atoms: Li occupies the totality of the 2a sites and Ni occupies statistically half of the 2b sites. Ti atoms are displaced from the center of octahedra units in alternating long (2.242 Å) and short (1.711 Å) Ti–O bonds along chains.

The X-ray powder diffraction patterns of three phenol derivatives—2-chlorophenol, 2,6-dichloro-4-nitrophenol, and 2,6-dichloro-phenoloindophenol tetrahydrate—were collected and the lattice parameters of these compounds were determined. The measurement for 2-chlorophenol was carried out at 250 K in a low-temperature chamber; this compound crystallizes in hexagonal system with a=1.59602(8) nm, c=0.59761(7) nm, space group P6 or P63/m. Investigated at room temperature, 2,6-dichloro-4-nitrophenol and 2,6-dichloro-phenoloindophenol tetrahydrate crystallize in the triclinic system with the unit cell parameters refined to a=0.8169(2) nm, b=1.6637(6) nm, c=0.7440(1) nm, α=96.6(3)°, β=116.19(2)°, γ=78.68°, and space group P-1(2), and a=0.7792(3) nm, b=1.2795(4) nm, c=0.7256(3) nm, α=91.17(5)°, β=96.93(4)°, γ=85.41(3)°, and space group P-1(2), respectively. © 2004 International Centre for Diffraction Data.

The theoretical concepts of the two methods are similar. Consequently, comparable fundamental parameter algorithms can be developed and applied to a quantitative analysis of bulk specimens and to an investigation of thin layers by TEY and by XRFA. Whereas the sampling depth of XRFA is determined by photoelectric absorption, for TEY the escape probability of electrons reduces this quantity to values of less than 100 nm. Thus, TEY is practically a surface analytical method with sampling depths between X-ray photoelectron spectrometry and XRFA. The decrease of fluorescence yields with decreasing atomic number Z is responsible for a significant reduction of the elemental sensitivity of XRFA in the range of low-Z elements. On the other hand, the elemental sensitivity of TEY increases with decreasing Z as a consequence of the dominating contribution of KLL- and LMM-Auger electrons to measured TEY jumps. The possibility to quantify submonolayers and layers of nm thickness buried under nm layers, a nearly linear dependence of TEY signals versus the elemental concentration of multielement specimens and the EXAFS and XANES information that is contained in measured TEY responses, are valuable features of TEY. A disadvantage of TEY is the time consuming sequential data accumulation of TEY spectra when compared to energy dispersive XRFA. But due to progress in instrumentation TEY is no longer reserved to synchrotron radiation sources

Two carbonates Cs2Sr2(CO3)3 and Rb2Sr2(CO3)3 were synthesized by solid-state reaction at high temperatures, and their crystal structures were determined from X-ray powder diffraction data. Because of the presence of heavy atoms and heavy peak overlapping, proper restrains on light-atom groups were found essential to obtain satisfactory results. The title compounds are isostructural to an early reported compound Cs2Ba2(CO3)3 and crystallize in cubic space group I213, with unit-cell dimensions a=10.072 64(2) Å for the cesium phase and a=9.855 56(7) Å for the rubidium phase. Unlike most carbonates, the title compounds feature in mutually perpendicular CO3 atomic groups. Our results also indicate that the global instability index is a more sensitive parameter in evaluating the structure rationality over the agreement factors. Moreover, differential thermal analysis and thermogravimetric analysis measurements reveal that Cs2Sr2(CO3)3 and Rb2Sr2(CO3)3 are stable in air up to 796 and 880 °C, respectively.

X-ray powder diffraction was used for the structural study of nonlinear optical borates K1−xNaxSr4(BO3)3 (x≤0.5). Results show that up to 50% K+ can be substituted by Na+ in orthorhombic K1−xNaxSr4(BO3)3. Isolated BO3 triangles in the Na-substituted compound constrict to adjust to a local distribution of alkali-metal atoms, which explains the large range of structural homogeneity. An expansion of the c axis in a unit cell with increasing Na substitution was found probably caused by the tilted BO3 triangles and asymmetric distortion of (K/Na)O8 polyhedra. As the ratio of ionic radii of alkaline-earth and alkali-metal cations decreases and the electronegative difference between alkaline-earth and alkali-metal cations increases, the crystal system of MM′4(BO3)3 borates changes from cubic to orthorhombic and then to monoclinic.

The crystal structure of anhydrous δ-D-mannitol (C6H14O6) was solved from high-resolution synchrotron X-ray powder diffraction data collected on a mixture containing 20% and 80% w/w of β- and δ-D-mannitol, respectively. The direct space simulated annealing program PSSP, and Rietveld analysis employing GSAS were used to determine and refine the structure. The polymorph has monoclinic symmetry, space group P21 with a=5.089 41(5) Å, b=18.2504(2) Å, c=4.917 02(5) Å, and β=118.303(2)°. There is one molecule in the irreducible volume of the unit cell. The pattern of hydrogen bonding is significantly different than the previously known α and β forms.

A neutron powder diffraction study on the crystal structure of the title compound (p-Br–C6D4–CD2–OD) confirmed that a first-order phase transition at Tt1=229 K accompanied a drastic change in the molecular conformation caused by a discontinuous rotational shift of the hydroxyl hydrogen atom around the C(D2)–O(D) bond. At T<Tt1, a contraction of the unit cell volume of ∼1% was found when compared to that of the normal compound (p-Br–C6H4–CH2–OH).