scholarly journals Continuous series of symmetric peak profile functions determined by standard deviation and kurtosis

2021 ◽  
pp. 1-11
Author(s):  
Takashi Ida
Keyword(s):  
Standard Deviation ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Practical Method ◽  
Continuous Series ◽  
Powder Diffraction Data ◽  
Lorentzian Function ◽  
Mathematical System ◽  
Truncated Gaussian

A mathematical system for modeling the effects of symmetrized instrumental aberrations has been developed. The system is composed of the truncated Gaussian, sheared Gaussian, and Rosin-Rammler-type functions. The shape of the function can uniquely be determined by the standard deviation and kurtosis. A practical method to evaluate the convolution with the Lorentzian function and results of application to the analysis of experimental powder diffraction data are briefly described.

FIDDLE. Simultaneous Indexing and Structure Solution from Powder Diffraction Data using a Genetic Algorithm and Correlation Functions

2019 ◽  
Author(s):  
Carmen Guguta ◽  
Jan M.M. Smits ◽  
Rene de Gelder
Keyword(s):  
Genetic Algorithm ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Correlation Functions ◽  
Cross Correlation ◽  
Simultaneous Optimization ◽  
Powder Diffraction Data ◽  
Structure Solution ◽  
Matching Technique

A method for the determination of crystal structures from powder diffraction data is presented that circumvents the difficulties associated with separate indexing. For the simultaneous optimization of the parameters that describe a crystal structure a genetic algorithm is used together with a pattern matching technique based on auto and cross correlation functions.<br>

Use of TALP with laboratory powder diffraction data from 2D detectors

2013 ◽  
Vol 28 (S2) ◽  
pp. S481-S490
Author(s):  
Oriol Vallcorba ◽  
Anna Crespi ◽  
Jordi Rius ◽  
Carles Miravitlles
Keyword(s):  
Organic Compounds ◽  
Structural Study ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Powder Pattern ◽  
Experimental Setup ◽  
Intensity Data ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Molecular Compounds

The viability of the direct-space strategy TALP (Vallcorba et al., 2012b) to solve crystal structures of molecular compounds from laboratory powder diffraction data is shown. The procedure exploits the accurate metric refined from a ‘Bragg-Brentano’ powder pattern to extract later the intensity data from a second ‘texture-free’ powder pattern with the DAJUST software (Vallcorba et al., 2012a). The experimental setup for collecting this second pattern consists of a circularly collimated X-ray beam and a 2D detector. The sample is placed between two thin Mylar® foils, which reduces or even eliminates preferred orientation. With the combination of the DAJUST and TALP software a preliminary but rigorous structural study of organic compounds can be carried out at the laboratory level. In addition, the time-consuming filling of capillaries with diameters thinner than 0.3mm is avoided.

Gaining insights into the evolutionary behaviour in genetic algorithm calculations, with applications in structure solution from powder diffraction data

2002 ◽  
Vol 353 (3-4) ◽  
pp. 185-194 ◽  
Author(s):  
Scott Habershon ◽  
Kenneth D.M. Harris ◽  
Roy L. Johnston ◽  
Giles W. Turner ◽  
Jennifer M. Johnston
Keyword(s):  
Genetic Algorithm ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Powder Diffraction Data ◽  
Structure Solution

Solving a superstructure from two-wavelength x-ray powder diffraction data - a simulation

2003 ◽  
Vol 12 (3) ◽  
pp. 310-314
Author(s):  
Chen Jian-Rong ◽  
Gu Yuan-Xin ◽  
Fan Hai-Fu
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Powder Diffraction Data ◽  
X Ray

Crystallographic study of ternary ordered skutterudite IrGe1.5Se1.5

2010 ◽  
Vol 25 (3) ◽  
pp. 247-252 ◽  
Author(s):  
F. Laufek ◽  
J. Návrátil
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Method ◽  
Crystallographic Data ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Crystallographic Study ◽  
Related Phase ◽  
The Ideal

The crystal structure of skutterudite-related phase IrGe1.5Se1.5 has been refined by the Rietveld method from laboratory X-ray powder diffraction data. Refined crystallographic data for IrGe1.5Se1.5 are a=12.0890(2) Å, c=14.8796(3) Å, V=1883.23(6) Å3, space group R3 (No. 148), Z=24, and Dc=8.87 g/cm3. Its crystal structure can be derived from the ideal skutterudite structure (CoAs3), where Se and Ge atoms are ordered in layers perpendicular to the [111] direction of the original skutterudite cell. Weak distortions of the anion and cation sublattices were also observed.

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