Texture and structural refinement using neutron diffraction data from molybdite (MoO₃) and calcite (CaCO₃) powders and a Ni-rich Ni_50.7Ti_49.30alloy

Abstract

Preferred orientation or texture is a common feature of experimental powder patterns. The mathematics of two commonly used models for preferred orientation-the March-Dollase and the generalized spherical-harmonic models-is reviewed. Both models were applied individually to neutron powder data from uniaxially pressed molybdite ͑MoO 3 ͒ and calcite ͑CaCO 3 ͒ powders in Rietveld analyses, as well as the as-received powders. The structural refinement results are compared to single-crystal structures. The results indicate that reasonable refinement of crystal structures can be obtained using either the March model or generalized spherical-harmonic description. However, the generalized spherical-harmonic description provided better Rietveld fits than the March model for the molybdite and calcite. Therefore, the generalized spherical-harmonic description is recommended for correction of preferred orientation in neutron diffraction analysis for both crystal structure refinement and phase composition analysis. Subsequently, the generalized spherical-harmonic description is extended to crystal structure refinement of annealed and the aged polycrystalline Ni-rich Ni 50.7 Ti 49.30 shape memory alloys. © 2009 International Centre for Diffraction Data.

Centimeter-Scale Synthesis of Ultrathin Layered MoO3 by van der Waals Epitaxy

“…To gain understanding of our experimental findings we compare with density functional theory (DFT) calculations of both bulk and monolayer MoO3. Our structural relaxations, obtained using the PBEsol functional, yield in-plane lattice constants within 2% error with respect to the bulk experimental values (see Table 1) , 27,28 Chem. Mater., 2016, 28 (11), pp 4042-4051 DOI: 10.1021/acs.chemmater.6b01505 Which has been published in final form at: http:// http://pubs.acs.org/doi/abs/10.1021/acs.chemmater.6b01505 11 bulk.…”

“…MoO3 lattice parameters. 27,28 Note that van der Waals correction has a sizable influence in the c parameter in the bulk structure, as has previously shown in Ref. 46 .…”

Mineralization of gellan gum hydrogels with calcium and magnesium carbonates by alternate soaking in solutions of calcium/magnesium and carbonate ion solutions

“…The phase content analysis was performed using the semiquantative Rietveld method. The theoretical CaCO 3 spectra were taken from the works of Sitepu () and Le Bail, Ouhenia, and Chateigner () for calcite and vaterite, respectively. The theoretical spectra of sodium chloride and magnesium calcite were taken from Strel'tsov, Tsirel'son, Ozerov, and Golovanov () and Althoff (), respectively.…”

Application of a New Method in Identifying the Sludge Deposits from Refineries and Gas Plants: A Case of Laboratory-Based Study

“…If the sample preparation is taken with great care, XRD provides accurate information on phase identification [8], Figure 2(b). When all the phases are identified accurately, the Rietveld method [9][10][11] can be used to perform the crystal structures [12], crystallographic preferred orientations [13], and quantitative phase analysis [14][15][16][17] of XRD data of crystalline materials. Additionally, the other structural parameters, such as average grain size, crystallinity, strain, and crystal defects can also be determined if they are required.…”