scholarly journals Use of Precession Electron and X Powder for solution and refinement of materials

2014 ◽  
Vol 70 (a1) ◽  
pp. C927-C927
Author(s):  
Marie Colmont ◽  
Lukas Palatinus ◽  
Marielle Huvé ◽  
Olivier Mentré ◽  
Pascal Roussel
Keyword(s):  
Ab Initio ◽  
Title Compound ◽  
Rietveld Method ◽  
Structural Type ◽  
A Posteriori ◽  
New Materials ◽  
X Ray ◽  
3D Tomography ◽  
System A

This communication will present the case study of ALa5O5(VO4)2 (A= Li, Na, K, Rb), example of the use of a combination of Precession Electron and X-ray Powder Data for the solution and the refinement of new materials. Indeed, an original structural type has been evidenced in the system (A, La, V, O) with A=Li, Na, K, Rb. Attempts to solve the structure ab initio on X-ray powder data were unsuccessful (more particularly because the powder was a mixture of the title compound and of unreacted precursors). The structure was finally solved by charge flipping using Precession Electron Data (3D tomography) on a nanocrystal, enabling a posteriori the good formulation of a pure powder. This powder was then classically refined by Rietveld method showing the correctness of the electron-solved structure. It crystallizes in a monoclinic unit cell with space group C2/m and a=20.2282(14) b=5.8639(4) c=12.6060(9) Å and β=117.64(1)0. The ALa5O5(VO4)2 structure is built of (OLa4) tetrahedral units creating Crenel-like 2D ribbons. These ribbons, surrounded by four isolated VO4 tetrahedra, are creating channels parallel to b axis in which A+ ions are located.

scholarly journals Portland clinker with civil construction waste: influence of pellet geometry on the formation of crystalline phases

2020 ◽  
Vol 20 (4) ◽  
pp. 205-223
Author(s):  
Fernanda Nepomuceno Costa ◽  
Daniel Véras Ribeiro ◽  
Cléber Marcos Ribeiro Dias
Keyword(s):  
Sustainable Development ◽  
Portland Cement ◽  
Rietveld Method ◽  
Industrial Process ◽  
3D Printer ◽  
New Materials ◽  
X Ray Diffraction ◽  
Construction Waste ◽  
X Ray ◽  
Portland Cement Association

Abstract Efforts to reduce greenhouse gas emissions in the context of sustainable development have intensified, with the development of research aimed at the production of new materials and binders for construction. This article analyzes the influence of pellet geometry in the production of clinkers, with the incorporation of construction waste (CCW). Procedures adapted from the method proposed by Brazilian Portland Cement Association were adopted in studies of laboratory clinkers, in an attempt to simulate the stages of the industrial process. Pellets were prepared with the same formulation, however, with four different geometries: spherical, with diameters of 1 cm, 2 cm and 3 cm, with manual molding, and semi-spherical, with a diameter of 2 cm, using molds of PLA (polylactic acid) printed on a 3D printer to facilitate the molding of the clinkers in a standardized way. Clinkers were characterized mineralogically by x-ray diffraction (XRD) and the Rietveld method was used to quantify the phases. Variations in the quantities of the alite and belite phases were observed depending on the geometry of the pellets, although the same calcination conditions were used. This is probably due to the variation in the surface area (exposure area) and the gradients of the cooling rate.

Comparison of multireference ab initio wavefunction methodologies for X-ray absorption edges: A case study on [Fe(II/III)Cl4]2–/1– molecules

2019 ◽  
Vol 150 (10) ◽  
pp. 104106 ◽  
Author(s):  
Dimitrios Maganas ◽  
Joanna K. Kowalska ◽  
Marcel Nooijen ◽  
Serena DeBeer ◽  
Frank Neese
Keyword(s):  
Ab Initio ◽  
X Ray ◽  
X Ray Absorption ◽  
Absorption Edges

Structures of two new high-pressure forms of AlPO4 by X-ray powder diffraction and NMR spectroscopy

2011 ◽  
Vol 67 (1) ◽  
pp. 30-40 ◽  
Author(s):  
Masami Kanzaki ◽  
Xianyu Xue ◽  
Sindy Reibstein ◽  
Eleanor Berryman ◽  
Seonyi Namgung
Keyword(s):  
High Pressure ◽  
Nmr Spectroscopy ◽  
Ab Initio ◽  
Crystal Structures ◽  
Powder Diffraction ◽  
Structure Determination ◽  
Rietveld Method ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
X Ray

The crystal structures of two new high-pressure AlPO4 phases are reported. One phase synthesized at 6 GPa and 1523 K is triclinic (P\bar 1) whilst the other phase synthesized at 7 GPa and 1773 K is monoclinic (P2_1/c). 31P MAS (magic-angle spinning) NMR suggests three tetrahedral P sites with equal abundance in both phases. 27Al 3Q MAS NMR spectra provided evidence for two octahedral sites and one five-coordinated Al site in each phase. The crystal structures were solved using an ab initio structure determination technique from synchrotron powder X-ray diffraction data utilizing the local structural information from NMR, and were further refined by the Rietveld method. Both phases contain doubly bent chains made of six edge-shared Al polyhedra (including five-coordinated Al), which are joined by PO4 tetrahedra. The P\bar{1} phase is isostructural with FeVO4 and AlVO4. The two phases differ in the packing manner of the chains. This study has demonstrated that the combined application of ab initio structure determination via X-ray powder diffraction and solid-state NMR spectroscopy is a powerful approach to the rapid solution of complex inorganic crystal structures.

Ab initio determination and Rietveld refinement of the crystal structure of Ni0.50TiO(PO4)

1999 ◽  
Vol 14 (1) ◽  
pp. 10-15 ◽  
Author(s):  
P. Gravereau ◽  
J. P. Chaminade ◽  
B. Manoun ◽  
S. Krimi ◽  
A. El Jazouli
Keyword(s):  
Crystal Structure ◽  
Ab Initio ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Method ◽  
Heavy Atom ◽  
Monoclinic Space Group ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Heavy Atom Method

The structure of the oxyphosphate Ni0.50TiO(PO4) has been determined ab initio from conventional X-ray powder diffraction data by the “heavy atom” method. The cell is monoclinic (space group P21/c, Z=4) with a=7.3830(5) Å, b=7.3226(5) Å, c=7.3444(5) Å, and β=120.233(6)°. Refinement of 46 parameters by the Rietveld method, using 645 reflexions, leads to cRwp=0.152, cRp=0.120, and RB=0.043. The structure of Ni0.50TiO(PO4) can be described as a TiOPO4 framework constituted by chains of tilted corner-sharing TiO6 octahedra running parallel to the c axis, crosslinked by phosphate tetrahedra and in which one-half of octahedral cavities created are occupied by Ni atoms. Ti atoms are displaced from the center of octahedra units in alternating long (2.231) and short (1.703 Å) Ti–O bonds along chains.

Ab initio determination and Rietveld refinement of the crystal structure of Ba7Cl2F12

1998 ◽  
Vol 13 (3) ◽  
pp. 152-156 ◽  
Author(s):  
B. Es-Sakhi ◽  
P. Gravereau ◽  
C. Fouassier
Keyword(s):  
Crystal Structure ◽  
Ab Initio ◽  
Rietveld Method ◽  
Heavy Atom ◽  
The Other ◽  
Halide Ions ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Heavy Atom Method ◽  
Trigonal Prisms

The structure of Ba7Cl2F12 has been determined ab initio from conventional X-ray powder diffraction data by the “heavy atom” method. The cell is hexagonal (space group P6¯, Z=1), with a=10.6373(2) Å and c=4.1724(2) Å. Refinement of 38 parameters by the Rietveld method, using 278 reflections, leads to cRwp=0.173, cRp=0.135, and RB=0.054. The structure has common characteristics with that of the other BaF2-rich fluorochloride, Ba12Cl5F19. In both phases Ba2+ ions lie in tricapped trigonal prisms formed by nine halide ions, and Cl− ions occupy the center of trigonal prisms of Ba2+ ions. F− ions are located in cationic tetrahedra or square pyramids.

In situX-ray diffraction analysis of iron ore sinter phases

2004 ◽  
Vol 37 (3) ◽  
pp. 362-368 ◽  
Author(s):  
Nicola V. Y. Scarlett ◽  
Ian C. Madsen ◽  
Mark I. Pownceby ◽  
Axel N. Christensen
Keyword(s):  
Iron Ore ◽  
Rietveld Method ◽  
Structural Type ◽  
X Ray Diffraction ◽  
X Ray ◽  
Intermediate Phases ◽  
Iron Ore Sinter ◽  
Phase Quantification ◽  
Bonding Phase

Owing to the depletion of world lump iron ore stocks, pre-treated agglomerates of fine ores are making up a growing proportion of blast-furnace feedstock (∼80%). These agglomerations, or `sinters', are generally composed of iron oxides, ferrites (most of which are silicoferrites of calcium and aluminium, SFCAs), glasses and dicalcium silicates (C2S). SFCA is the most important bonding phase in iron ore sinter, and its composition, structural type and texture greatly affect its physical properties. Despite its prevalence and importance, the mechanism of SFCA formation is not fully understood.In situpowder X-ray diffraction investigations have been conducted into the formation of SFCA, allowing the study of the mechanism of its formation and the observation of intermediate phases with respect to time and temperature. Studies have been carried out to investigate the effects of changing the substitution levels of aluminium for iron. The use of the Rietveld method for phase quantification gives an indication of the order and comparative rates of phase formation throughout the experiments.

Crystal structure and powder diffraction pattern of high-temperature modification of Pd73Sn14Te13

2007 ◽  
Vol 22 (4) ◽  
pp. 334-339 ◽  
Author(s):  
F. Laufek ◽  
A. Vymazalová ◽  
J. Plášil
Keyword(s):  
Crystal Structure ◽  
High Temperature ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Title Compound ◽  
Rietveld Method ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Temperature Modification ◽  
High Temperature Modification

Crystal structure of high-temperature modification of Pd73Sn14Te13 has been refined by the Rietveld method from laboratory X-ray powder diffraction data. Refined crystallographic data of Pd73Sn14Te13 are a=7.6456(3) Å, c=13.9575(9) Å, V=706.75(6) Å3, space group P63cm (No. 185), Z=6, and Dx=10.71 g/cm3. The title compound is isostructural with Pd5Sb2 and Ni5As2; it can be considered as a stacking and filling variant of the Ni2In structure. An important structural feature in the high-temperature modification of Pd73Sn14Te13 is the presence of various Pd-Pd bonds.

Structure of [Pd(NH3)4]Cr2O7

1995 ◽  
Vol 10 (3) ◽  
pp. 159-164 ◽  
Author(s):  
Y. Laligant ◽  
A. Le Bail
Keyword(s):  
Hydrogen Bonds ◽  
Ab Initio ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Method ◽  
Monoclinic Space Group ◽  
Powder Diffraction Data ◽  
Hydrogen Atoms ◽  
Space Group ◽  
X Ray

The structure of [Pd(NH3)4]Cr2O7 has been determined ab initio from conventional X-Ray powder diffraction data by the Patterson method. The cell is monoclinic (space group P21/c, Z = 4), with a = 7.771(3) Å, b=11.578(1) Å, c=11.852(4) Å, and β= 105.50(4)°. Refinements of 57 parameters by the Rietveld method, using 852 reflections lead to RB = 0.032, RP = 0.075, and Rwp = 0.092. The structure is built up from PdN4 square planes linked to Cr2O7 groups by hydrogen bonds. Hydrogen atoms could not be located.

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