EXPO2011 is a new package for phasing crystal structures from powder diffraction diagrams. It is able to carry out all the steps necessary for crystal structure solution, from pattern indexation up to Rietveld method for structure refinement: for each step, the basic algorithm is described. Phasing is performed via ab initio (e.g., Direct Methods, integrated by real space refinement) and non ab initio techniques (e.g., simulated annealing algorithm, when molecular geometry is a priori known). Some emphasis is given to running procedures: the main commands and directives are described, to allow the user to run default and non-default phasing attempts.

Rigid bodies provide a way to simplify the model used in a crystallographic refinement by removing parameters that describe degrees of freedom that are unlikely to change based on chemical experience. The GSAS software package provides a powerful implementation of rigid bodies that allows for refinement of classes of bond lengths, grouping of bodies to further reduce parameterization and where atomic motion can be described from group displacement parameters (TLS) representation. However, use of rigid bodies in GSAS is complex to learn and time-consuming to perform. This paper describes how the rigid body definition process has been simplified and extended through implementation in the EXPGUI interface to GSAS.

Computer algebra removes much of the drudgery from mathematics; it allows users to formulate models by using the language of mathematics and to have those models evaluated with little effort. This symbolic form of representation is often thought of as being separate to dedicated computational programs such as Rietveld refinement. These dedicated programs are often written in low level languages; they are relatively inflexible in what they do and modifying them to change functionality in a small manner is often a major programming task. This paper describes a symbolic system that is integrated into the dedicated Rietveld refinement program called TOPAS. The symbolic component allows large functional changes to be made at run time and with a relatively small amount of effort. In addition, the system as a whole reduces the programming complexity at the developmental stage.

Two applications of parametric Rietveld refinement employing a newly developed robust computer program are presented. The first application focuses on the parametric kinetic analysis of the reactions involving phase transitions of various polymorphic forms of copper phthalocyanine pigments. The second application concerns the parameterization of crystallite size with respect to experimental temperature. XRPD data for nanocrystalline titanium dioxide measured in dependence on temperature are used in this case study. Both the applications were realized with the help of the developed program in combination with the launch mode of topas® software.

Crystal structure of Ca1-x/2AlSi(N3-xOx):Eu2+ (x ∼ 0.11) has been characterized using an X-ray powder diffractometer and a transmission electron microscope equipped with an energy dispersive X-ray analyzer (EDX) and an electron energy loss spectrometer (EELS). The title compound is orthorhombic with space group Cmc21, Z = 4, unit-cell dimensions a = 0.979780(7) nm, b = 0.565197(4) nm, c = 0.506356(3) nm, and V = 0.280404(3) nm3. The atom ratio Al:Si was determined to be 1:1 by EDX, and the presence of O atoms in the crystal structure was confirmed by EELS. The x-value and the atomic coordinates of the final structural model were determined by the Rietveld method. The maximum-entropy methods-based pattern fitting (MPF) method was used to confirm the validity of the structural model, in which conventional structure bias caused by assuming intensity partitioning was minimized. The reliability indices calculated from MPF are Rwp = 9.18%, S = 1.17, Rp = 6.77%, RB = 1.91%, and RF = 0.86%. Atomic arrangements of the final structural model are in an excellent agreement with the three dimensional electron-density distributions determined by MPF.

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].

CdTe nanorods and various branched nanostructures with different crystal structures were have successfully prepared via the catalyst-assisted vacuum thermal evaporation (CVTE) technique using various experimental parameters. SEM and XRD studies were carried out on the as-prepared CdTe nanostructures. The results show that the morphologies and crystal structures of the products were strongly influenced by the growth conditions and the mole ratios of Bi and CdTe. In the high mole ratio (0.08:1) of Bi and CdTe, CdTe branched nanostructures of CdTe were obtained, while nanorods of CdTe were formed at a lower mole ratio of 0.05:1. The crystal structure of products is either Zinc blende or a two-phase mixture of zinc blende and wurtzite. The content of the wurtzite phase were found to increase with increasing growth temperature. Our results also reveal that high growth temperature tends to form the wurtzite phase, and stacking faults may exist in materials grown in higher temperatures. These nanostructures grow following the vapor–liquid–solid (VLS) mechanism.

Two new bimetallic and trimetallic compounds (NH4)1.5Ni2V2O7(OH)1.5 · H2O and (NH4)1.5Cu1.125 Ni1.125V2O7(OH)2 · H2O were synthesized by hydrothermal method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and X-Ray fluorescence (XRF). Crystallographic studies showed that both compounds are hexagonal with space group P-62c.

The 7-methyl-cis-2-(1’-naphthyl)-2,3,4,5-tetrahydro-1H-benzo[b]azepin-4-ol (chemical formula C21H21NO) was prepared via the reductive cleavage of the bridged N-O bond of the corresponding 7-methyl-2-exo-(1′-naphthyl)-1,4-epoxytetrahydro-1-benzazepine. The X-ray powder diffraction pattern for the new compound was analyzed and found that the title compound crystallizes in a monoclinic system with space group P2/c (No. 13) and refined unit-cell parameters a = 11.012(2), b = 18.613(5), c = 7.316(4) Å, β = 102.88(3) ° and V = 1461.8(7) Å3.