scholarly journals SUPERFLIP– a computer program for the solution of crystal structures by charge flipping in arbitrary dimensions

2007 ◽  
Vol 40 (4) ◽  
pp. 786-790 ◽  
Author(s):  
Lukáš Palatinus ◽  
Gervais Chapuis
Keyword(s):  
Computer Program ◽  
Crystal Structures ◽  
Diffraction Data ◽  
Periodic Structures ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Modulated Structures ◽  
Structure Solution ◽  
Matching Procedure ◽  
Arbitrary Dimensions

SUPERFLIPis a computer program that can solve crystal structures from diffraction data using the recently developed charge-flipping algorithm. It can solve periodic structures, incommensurately modulated structures and quasicrystals from X-ray and neutron diffraction data. Structure solution from powder diffraction data is supported by combining the charge-flipping algorithm with a histogram-matching procedure.SUPERFLIPis written in Fortran90 and is distributed as a source code and as precompiled binaries. It has been successfully compiled and tested on a variety of operating systems.

scholarly journals Solving molecular crystal structures from laboratory X-ray powder diffraction data withDASH: the state of the art and challenges

2005 ◽  
Vol 38 (2) ◽  
pp. 249-259 ◽  
Author(s):  
Alastair J. Florence ◽  
Norman Shankland ◽  
Kenneth Shankland ◽  
William I. F. David ◽  
Elna Pidcock ◽  
...  
Keyword(s):  
Global Optimization ◽  
Crystal Structures ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Degrees Of Freedom ◽  
Search Space ◽  
Powder Diffraction Data ◽  
Multi Centre Study ◽  
X Ray ◽  
Structure Solution

The crystal structures of 35 molecular compounds have been redetermined from laboratory monochromatic capillary transmission X-ray powder diffraction data using the simulated-annealing approach embodied within theDASHstructure solution package. The compounds represent industrially relevant areas (pharmaceuticals; metal coordination compounds; nonlinear optical materials; dyes) in which the research groups in this multi-centre study are active. The molecules were specifically selected to form a series within which the degree of structural complexity (i.e. degrees of freedom in the global optimization) increased systematically, the degrees of freedom increasing with increasing number of optimizable torsion angles in the structural model and with the inclusion of positional disorder or multiple fragments (counterions; crystallization solvent;Z′ > 1). At the lower end of the complexity scale, the structure was solved with excellent reproducibility and high accuracy. At the opposite end of the scale, the more complex search space offered a significant challenge to the global optimization procedure and it was demonstrated that the inclusion of modal torsional constraints, derived from the Cambridge Structural Database, offered significant benefits in terms of increasing the frequency of successful structure solution by restricting the magnitude of the search space in the global optimization.

scholarly journals PSSP, a computer program for the crystal structure solution of molecular materials from X-ray powder diffraction data

2010 ◽  
Vol 43 (2) ◽  
pp. 370-376 ◽  
Author(s):  
Silvina Pagola ◽  
Peter W. Stephens
Keyword(s):  
Crystal Structure ◽  
Computer Program ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Degrees Of Freedom ◽  
Space Structure ◽  
Molecular Solids ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Structure Solution

This work describes the computer programPSSP(powder structure solution program) for the crystal structure solution of molecular solids from X-ray powder diffraction data. This direct-space structure solution program uses the simulated annealing global optimization algorithm to minimize the difference between integrated intensities calculated from trial models and those extracted in a Le Bail fit of the experimental pattern, using a cost function for dealing with peak overlap through defined intensity correlation coefficients, computationally faster to calculate thanRwp. The methodology outlined is applicable to organic solids composed of moderately complex rigid and flexible molecules, using diffraction data up to relatively low resolution.PSSPperformance tests using 11 molecular solids with six to 20 degrees of freedom are analyzed.

The crystal structures of solvent-free alkali-metal squarates from powder diffraction data

2005 ◽  
Vol 220 (11) ◽  
Author(s):  
Robert E. Dinnebier ◽  
Hanne Nuss ◽  
Martin Jansen
Keyword(s):  
High Resolution ◽  
Alkali Metal ◽  
Crystal Structures ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Room Temperature ◽  
Solvent Free ◽  
Crystallographic Data ◽  
Powder Diffraction Data ◽  
X Ray

AbstractThe crystal structures of solvent-free lithium, sodium, rubidium, and cesium squarates have been determined from high resolution synchrotron and X-ray laboratory powder patterns. Crystallographic data at room temperature of Li

The BaAl4 Structure and its Derivatives from the R-Zn-Ga Systems

2012 ◽  
Vol 194 ◽  
pp. 5-9 ◽  
Author(s):  
Yuriy Verbovytskyy ◽  
Antonio Pereira Gonçalves
Keyword(s):  
Crystal Structures ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Powder Diffraction Data ◽  
Space Group ◽  
X Ray ◽  
First Time

Seven new ternary RZn1+xGa3-x (R = Ce, Pr, Nd, Sm, Ho and Er) and R5Zn2Ga17 (R = Ce) phases are synthesized for the first time. Their crystal structures are solved on basis of X-ray powder diffraction data. The above mentioned compounds belong to the BaAl4 (space group I4/mmm) and Rb5Hg19 (space group I4/m) structure types. Details of the structure of the Ce5Zn2Ga17 compound and relationship with RZn2-xGa2+x (BaAl4 type) and R3Zn8-xGa3+x (La3Al11 type) are briefly discussed.

Update in a Rietveld analysis program for x-ray powder spectro-diffractometry

2003 ◽  
Vol 18 (1) ◽  
pp. 32-35 ◽  
Author(s):  
Yanan Xiao ◽  
Fujio Izumi ◽  
Timothy Graber ◽  
P. James Viccaro ◽  
Dale E. Wittmer
Keyword(s):  
Computer Program ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Analysis ◽  
Anomalous Scattering ◽  
Analysis Program ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Synchrotron Light ◽  
Diffraction Patterns

A computer program for refining anomalous scattering factors using x-ray powder diffraction data was revised on the basis of the latest version of a versatile pattern-fitting system, RIETAN-2000. The effectiveness of the resulting program was confirmed by applying it to simulated and measured powder-diffraction patterns of Mn3O4 taken at a synchrotron light source.

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