scholarly journals The Rietveld Refinement in the EXPO Software: A Powerful Tool at the End of the Elaborate Crystal Structure Solution Pathway

Crystals ◽  
2018 ◽  
Vol 8 (5) ◽  
pp. 203 ◽  
Author(s):  
Angela Altomare ◽  
Francesco Capitelli ◽  
Nicola Corriero ◽  
Corrado Cuocci ◽  
Aurelia Falcicchio ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Rietveld Refinement ◽  
Structure Solution

Crystal structure of copper(ii) citrate monohydrate solved from a mixture powder X-ray diffraction pattern

2013 ◽  
Vol 29 (1) ◽  
pp. 28-32 ◽  
Author(s):  
Ana Palčić ◽  
Ivan Halasz ◽  
Josip Bronić
Keyword(s):  
Crystal Structure ◽  
Diffraction Pattern ◽  
Rietveld Refinement ◽  
Powder Diffraction ◽  
X Ray Diffraction ◽  
X Ray ◽  
Indexing Structure ◽  
Pattern Approach ◽  
Structure Solution ◽  
Diffraction Patterns

The crystal structure of copper(ii) citrate monohydrate (C6H4O7Cu2·H2O) has been solved from a mixture powder diffraction pattern. Approach to indexing, structure solution and Rietveld refinement of multiphase diffraction patterns is discussed. Rietveld refinement is carried out employing free-atom refinement and rigid body refinement.

scholarly journals Structure of Pigment Yellow 181 dimethylsulfoxideN-methyl-2-pyrrolidone (1:1:1) solvate from XRPD + DFT-D

2015 ◽  
Vol 71 (1) ◽  
pp. 89-94 ◽  
Author(s):  
Jacco van de Streek
Keyword(s):  
Crystal Structure ◽  
Simulated Annealing ◽  
Rietveld Refinement ◽  
Density Functional ◽  
Degrees Of Freedom ◽  
Functional Theory ◽  
Structure Solution ◽  
Network Of Hydrogen Bonds ◽  
Three Stages ◽  
Solvent Molecules

With only a 2.6 Å resolution laboratory powder diffraction pattern of the θ phase of Pigment Yellow 181 (P.Y. 181) available, crystal-structure solution and Rietveld refinement proved challenging; especially when the crystal structure was shown to be a triclinic dimethylsulfoxideN-methyl-2-pyrrolidone (1:1:1) solvate. The crystal structure, which in principle has 28 possible degrees of freedom, was determined in three stages by a combination of simulated annealing, partial Rietveld refinement with dummy atoms replacing the solvent molecules and further simulated annealing. The θ phase not being of commercial interest, additional experiments were not economically feasible and additional dispersion-corrected density functional theory (DFT-D) calculations were employed to confirm the correctness of the crystal structure. After the correctness of the structure had been ascertained, the bond lengths and valence angles from the DFT-D minimized crystal structure were fed back into the Rietveld refinement as geometrical restraints (`polymorph-dependent restraints') to further improve the details of the crystal structure; the positions of the H atoms were also taken from the DFT-D calculations. The final crystal structure is a layered structure with an elaborate network of hydrogen bonds.

EXPO: a program for full powder pattern decomposition and crystal structure solution

1999 ◽  
Vol 32 (2) ◽  
pp. 339-340 ◽  
Author(s):  
Angela Altomare ◽  
Maria Cristina Burla ◽  
Mercedes Camalli ◽  
Benedetta Carrozzini ◽  
Giovanni Luca Cascarano ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Rietveld Refinement ◽  
Prior Information ◽  
Solution Process ◽  
Powder Pattern ◽  
Pattern Decomposition ◽  
Structure Solution

EXPOis the integration of two programs,EXTRAandSIRPOW.92, the first devoted to full powder pattern decomposition and the second to the solution and refinement of crystal structures. The program is able to exploit the prior information obtained during the crystal structure solution process for improving the classical decomposition.EXPOalso allows preliminary cycles of Rietveld refinement.

New similarity index for crystal structure determination from X-ray powder diagrams

2005 ◽  
Vol 38 (6) ◽  
pp. 861-866 ◽  
Author(s):  
Detlef Walter Maria Hofmann ◽  
Ludmila Kuleshova
Keyword(s):  
Crystal Structure ◽  
Structure Determination ◽  
Structure Prediction ◽  
Similarity Index ◽  
Crystal Structure Determination ◽  
Crystal Structure Prediction ◽  
X Ray ◽  
Organic Pigments ◽  
Structure Solution ◽  
Similarity Indices

A new similarity index for automated comparison of powder diagrams is proposed. In contrast to traditionally used similarity indices, the proposed method is valid in cases of large deviations in the cell constants. The refinement according to this index closes the gap between crystal structure prediction and automated crystal structure determination. The opportunities of the new procedure have been demonstrated by crystal structure solution of un-indexed powder diagrams of some organic pigments (PY111, PR181 and Me-PR170).

The crystal structure of Na(NH4)Mo3O10·H2O

2017 ◽  
Vol 32 (2) ◽  
pp. 140-147 ◽  
Author(s):  
Joel W. Reid ◽  
James A. Kaduk ◽  
Jeremy A. Olson
Keyword(s):  
Crystal Structure ◽  
Density Functional Theory ◽  
Rietveld Refinement ◽  
Software Package ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Parallel Tempering ◽  
Powder Diffraction Data ◽  
Functional Theory ◽  
Synchrotron Powder Diffraction

The crystal structure of Na(NH4)Mo3O10·H2O has been solved by parallel tempering using the FOX software package with synchrotron powder diffraction data obtained from beamline 08B1-1 at the Canadian Light Source. Rietveld refinement, performed with the software package GSAS, yielded orthorhombic lattice parameters of a = 13.549 82(10), b = 7.618 50(6), and c = 9.302 74(7) Å (Z = 4, space group Pnma). The structure is composed of molybdate chains running parallel to the b-axis. The Rietveld refinement results were compared with density functional theory calculations performed with CRYSTAL14, and show excellent agreement with the calculated structure.

Chemical reasonableness in Rietveld analysis; organics

2007 ◽  
Vol 22 (1) ◽  
pp. 74-82 ◽  
Author(s):  
James A. Kaduk
Keyword(s):  
Rietveld Refinement ◽  
Normal Values ◽  
Solution Process ◽  
Molecular Geometry ◽  
Rietveld Analysis ◽  
Rigid Bodies ◽  
Torsion Angles ◽  
Structure Solution ◽  
Calcium Tartrate

We know a lot about normal values of bond distances, bond angles, torsion angles, and other molecular parameters. This knowledge can be incorporated into the structure solution process and into Rietveld refinement through the use of restraints and rigid bodies. An important measure of the quality of the refined model is the chemical reasonableness of molecular geometry. Refinement of the structures of calcium tartrate tetrahydrate and guaifenesin is used to illustrate the importance of chemical reasonableness in determining the quality of a Rietveld refinement.

Using GPUs to compute fast Fourier transforms for crystal structure solution and refinement

2013 ◽  
Vol 46 (3) ◽  
pp. 594-600 ◽  
Author(s):  
ElSayed Mohamed Shalaby ◽  
Miguel Afonso Oliveira
Keyword(s):  
Crystal Structure ◽  
Fourier Transformation ◽  
Fourier Transforms ◽  
Fast Fourier Transformation ◽  
Parallel Calculations ◽  
The Past ◽  
Graphical Processing Units ◽  
Software Algorithms ◽  
Structure Solution ◽  
Graphical Processing

In the past few years, new hardware tools have become available for computing using the graphical processing units (GPUs) present in modern graphics cards. These GPUs allow efficient parallel calculations with a much higher throughput than microprocessors. In this work, fast Fourier transformation calculations used inSIR2011software algorithms have been carried out using the power of the GPU, and the speed of the calculations has been compared with that achieved using normal CPUs.

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