— The crystal structure of K2TiSi3O9•H2O has been solved ab initio from X-ray powder data. The unit cell is orthorhombic (space group P212121, Z = 4) with cell dimensions a = 7.1362(2) Å, b = 9.9084(3) Å, c = 12.9414(4) Å, V = 915.07 Å. The structural model was obtained from direct methods using 455 integrated intensities. The Rietveld refinement converged to final Bragg and profile indicators ...

Symmetry modes provide an alternative method to describe crystal structures. Using the fact that many crystal structures can be described as a distorted version of a higher symmetric parent structure, the traditional atomic positions, occupancies or lattice parameters are no longer used. Instead, all structural features are described applying symmetry modes. This can be of particular interest i...

Department of Physics, Shanghai University, Shanghai 200444, People’s Republic of China, Shanghai Key Laboratory of High-Temperature Superconductors, Shanghai 200444, People’s Republic of China, Department of Physics, California Institute of Technology, Pasadena, CA 91125, USA, National Laboratory for Superconductivity, Institute of Physics, Chinese Academy of Sciences, Beijing 100080, People’s...

— α-NaCaAlF6 is prepared by solid state reaction as poor quality crystals. The structure is determined ab initio from conventional X-ray powder data. The cell is monoclinic, space group P21/c, Z = 8, with a = 8.7423(3) Å, b = 5.1927(2) Å, c = 20.3514(9) Å and β = 91.499(2)°. The final Rietveld refinement leads to RP = 10.6 % and RB = 5.2 %. The structure is built up from isolated AlF6 octahedra...

We propose two improvements to the microstructural modeling in Rietveld refinement. The first is the model that yields the complete texture-weighted strain and stress tensors as a function of crystallite orientations, as well as the average values of macroscopic strain and stress tensors for all Laue classes. Implementation in the Rietveld refinement program can be made through the set of refin...

The paper addresses requirements for achieving Rietveld phase composition analysis (PCA) accuracy in the vicinity of 1% by weight with particular reference to scale factor precision. It is proposed from a statistical analysis that the target for scale factor estimated standard deviation (esd) should be in the vicinity of 0.2% relative, with additional targets being assumed for the ZMV factors, ...

The procedure for the quantitative phase analysis using the whole-powder-pattern decomposition method has been applied to ten-component mixtures of synthesized ceramic materials and a five-component mixture of natural products. Average deviations of the calculated weight fractions of respective phases from those prepared in mixing were within 1 weight percent (wt.%), and they were smaller than ...

We report on the residual stresses in amorphous shape memory polymers reinforced with SiC particles. After 50% compression of the composite material at 25 °C, the SiC particles exhibit a compressive stress, which is almost completely released during heated recovery at 120 °C. The residual stresses in SiC hexagonal (6H) phase were estimated through the average change of the unit-cell volume. Lat...

We have prepared polycrystalline samples of the trimer Ir oxide BaIrO3 with face-shared Ir3O12 trimers, and have investigated the origin of the phase transition at 182 K by measuring resistivity, thermopower, magnetization and synchrotron X-ray diffraction. We propose a possible electronic model and transition mechanism, starting from a localized electron picture on the basis of the Rietveld re...