Combined method forab initiostructure solution from powder diffraction data

1999 ◽  
Vol 32 (5) ◽  
pp. 864-870 ◽  
Author(s):  
H. Putz ◽  
J. C. Schön ◽  
M. Jansen
Keyword(s):  
Global Optimization ◽  
Potential Energy ◽  
Diffraction Pattern ◽  
Intermetallic Compounds ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Powder Diffraction Data ◽  
Combined Method ◽  
The Difference ◽  
Space Method

A new direct-space method forabinitiosolution of crystal structures from powder diffraction diagrams is presented. The approach consists of a combined global optimization (`Pareto optimization') of the difference between the calculated and the measured diffraction pattern and of the potential energy of the system. This concept has been tested successfully on a large variety of ionic and intermetallic compounds.

Challenging structure determination from powder diffraction data: two pharmaceutical salts and one cocrystal with Z′ = 2

2019 ◽  
Vol 234 (4) ◽  
pp. 257-268 ◽  
Author(s):  
Carina Schlesinger ◽  
Michael Bolte ◽  
Martin U. Schmidt
Keyword(s):  
Single Crystal ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Structure Determination ◽  
Real Space ◽  
Powder Diffraction Data ◽  
The Real ◽  
Pharmaceutical Salts ◽  
Structure Solution ◽  
Space Method

Abstract Structure solution of molecular crystals from powder diffraction data by real-space methods becomes challenging when the total number of degrees of freedom (DoF) for molecular position, orientation and intramolecular torsions exceeds a value of 20. Here we describe the structure determination from powder diffraction data of three pharmaceutical salts or cocrystals, each with four molecules per asymmetric unit on general position: Lamivudine camphorsulfonate (1, P 21, Z=4, Z′=2; 31 DoF), Theophylline benzamide (2, P 41, Z=8, Z′=2; 23 DoF) and Aminoglutethimide camphorsulfonate hemihydrate [3, P 21, Z=4, Z′=2; 31 DoF (if the H2O molecule is ignored)]. In the salts 1 and 3 the cations and anions have two intramolecular DoF each. The molecules in the cocrystal 2 are rigid. The structures of 1 and 2 could be solved without major problems by DASH using simulated annealing. For compound 3, indexing, space group determination and Pawley fit proceeded without problems, but the structure could not be solved by the real-space method, despite extensive trials. By chance, a single crystal of 3 was obtained and the structure was determined by single-crystal X-ray diffraction. A post-analysis revealed that the failure of the real-space method could neither be explained by common sources of error such as incorrect indexing, wrong space group, phase impurities, preferred orientation, spottiness or wrong assumptions on the molecular geometry or other user errors, nor by the real-space method itself. Finally, is turned out that the structure solution failed because of problems in the extraction of the integrated reflection intensities in the Pawley fit. With suitable extracted reflection intensities the structure of 3 could be determined in a routine way.

Organa– a program package for structure determination from powder diffraction data by direct-space methods

2005 ◽  
Vol 38 (4) ◽  
pp. 688-693 ◽  
Author(s):  
V. Brodski ◽  
R. Peschar ◽  
H. Schenk
Keyword(s):  
Potential Energy ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Structure Determination ◽  
Energy Function ◽  
Potential Energy Function ◽  
Van Der Waals Interactions ◽  
Powder Diffraction Data ◽  
Trial Structure ◽  
The Cost

A new software package has been developed, namedOrgana, forab initiosolution of crystal structures from powder diffraction data by direct-space methods. The package contains energy-guiding Monte Carlo and grid-search algorithms and is based on a combined global minimization of theRfactor and a potential energy function of the system with the option of local minimization of the cost function for each generated trial structure. Basically, the potential energy function consists of van der Waals interactions, but harmonic potentials can be added to impose soft distance restraints. The program was successfully applied to the structure determination of a series of melamine phosphate compounds. The program is freely available (for all Windows platforms) from the correspondence author upon request.

X-ray powder diffraction data for indium nitride

1999 ◽  
Vol 14 (4) ◽  
pp. 258-260 ◽  
Author(s):  
W. Paszkowicz
Keyword(s):  
Diffraction Pattern ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Microwave Plasma ◽  
Indium Nitride ◽  
Plasma Source ◽  
Unit Cell ◽  
Powder Diffraction Data ◽  
Calculated Density ◽  
X Ray

X-ray powder diffraction pattern for InN synthesized using a microwave plasma source of nitrogen is reported. The data were obtained with the help of an automated Bragg-Brentano diffractometer using Ni-filtered CuKα radiation. The lattice parameters for the wurtzite-type unit cell are ao=3.5378(1) Å, co=5.7033(1) Å. The calculated density is 6.921±0.002 g/cm3.

X-ray powder diffraction data for the superconducting phase Tl0.5Pb0.5Sr2CaCu2O6.5+δ

1993 ◽  
Vol 8 (4) ◽  
pp. 249-250 ◽  
Author(s):  
Chan Park ◽  
Robert L. Snyder
Keyword(s):  
High Temperature ◽  
Molten Salt ◽  
Diffraction Pattern ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Superconducting Phase ◽  
Powder Diffraction Data ◽  
X Ray ◽  
High Temperature Superconducting

The X-ray powder diffraction pattern for a sample of the high-temperature superconducting phase Tl0.5Pb0.5Sr2CaCu2O6.5+δ has been determined. The sample was prepared by a molten salt technique and had a Tc of 96 K.

X-Ray Powder Diffraction Data for Wolfeite: (Fe0.59Mn0.40Mg0.01)2PO4(OH)

1989 ◽  
Vol 4 (1) ◽  
pp. 34-35 ◽  
Author(s):  
Diano Antenucci ◽  
Francois Fontan ◽  
Andre-Mathieu Fransolet
Keyword(s):  
Federal Republic ◽  
Diffraction Pattern ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Unit Cell ◽  
Federal Republic Of Germany ◽  
Powder Diffraction Data ◽  
Unit Cell Parameters ◽  
X Ray ◽  
Cell Parameters

AbstractWolfeite (Fe0.59Mn0.40Mg0.01)2PO4(OH) from the Hagendorf-Sud pegmatite, Bavaria, Federal Republic of Germany, yields unit-cell parameters of: a = 12.319(1), b = 13.280(2), c = 9.840(1) Å and β = 108° 24(1). Dmeas. = 3.82(2); Dcalc. = 3.88. An indexed powder diffraction pattern is given.

A Monte Carlo approach to crystal structure determination from powder diffraction data

2003 ◽  
Vol 36 (2) ◽  
pp. 239-243 ◽  
Author(s):  
V. Brodski ◽  
R. Peschar ◽  
H. Schenk
Keyword(s):  
Crystal Structure ◽  
Monte Carlo ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Structure Determination ◽  
Global Minimization ◽  
Powder Diffraction Data ◽  
Unknown Structure ◽  
Space Method

A new direct-space method forab initiosolution of crystal structures from powder diffraction data is presented. The approach consists of a combined global minimization ofRwpand the potential energy of the system. This method was tested on two organic compounds with known structure and also applied successfully in the structure determination of the previously unknown structure of melamine pyrophosphate.

scholarly journals Structure determination from X-ray powder diffraction data at low resolution

2014 ◽  
Vol 70 (a1) ◽  
pp. C143-C143
Author(s):  
Hongliang Xu
Keyword(s):  
Single Crystal ◽  
Diffraction Pattern ◽  
Crystal Structures ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Structure Determination ◽  
Direct Methods ◽  
Atomic Resolution ◽  
Powder Diffraction Data ◽  
Low Resolution

Knowledge of the structural arrangement of atoms in solids is necessary to facilitate the study of their properties. The best and most detailed structural information is obtained when the diffraction pattern of a single crystal a few tenths of a millimeter in each dimension is analyzed, but growing high-quality crystals of this size is often difficult, sometimes impossible. However, many crystallization experiments that do not yield single crystals do yield showers of randomly oriented micro-crystals that can be exposed to X-rays simultaneously to produce a powder diffraction pattern. Direct Methods routinely solve crystal structures when single-crystal diffraction data are available at atomic resolution (1.0-1.2Å), but fail to determine micro-crystal structures due to reflections overlapping and low-resolution powder diffraction data. By artificially and intelligently extending the measured data to atomic resolution, we have successfully solved structures having low-resolution diffraction data that were hard to solve by other direct-method based computation procedures. The newly developed method, Powder Shake-and-Bake, is implemented in a computer program PowSnB. PowSnB can be incorporated into the state-of-the-art software package EXPO that includes powder data reduction, structure determination and structure refinement. The new combination could have potential to solve structures that have never been solved before by direct-methods approach.

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