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The use of computational methods for the powder X-ray diffraction data analysis is now generalized. It typically compares the experimental data to the simulated diffractogram of a model structure, taking into account the instrumental parameters, and refines the structural or microstructural parameters of the model using least squares based ...
The most common powder X-ray diffraction (XRD) refinement technique used today is based on the method proposed in the 1960s by Hugo Rietveld. [2] The Rietveld method fits a calculated profile (including all structural and instrumental parameters) to experimental data.
The Wyckoff positions are named after Ralph Wyckoff, an American X-ray crystallographer who authored several books in the field.His 1922 book, The Analytical Expression of the Results of the Theory of Space Groups, [3] contained tables with the positional coordinates, both general and special, permitted by the symmetry elements.
Patterns may be experimentally determined, or computed based on crystal structure and Bragg's law. It is most often used to identify substances based on x-ray diffraction data, and is designed for use with a diffractometer. The PDF contains more than a million unique material data sets.
In X-ray crystallography, the Flack parameter is a factor used to estimate the absolute configuration of a structural model determined by single-crystal structure analysis. In this approach, one determines the absolute structure of a crystal in a Sohncke Space group .
Crystallographic data are primarily extracted from published scientific articles and supplementary material. Newer versions of crystallographic databases are built on the relational database model, which enables efficient cross-referencing of tables. Cross-referencing serves to derive additional data or enhance the search capacity of the database.
In crystallography, the R-factor (sometimes called residual factor or reliability factor or the R-value or R Work) is a measure of the disagreement between the crystallographic model and the experimental X-ray diffraction data - lower the R value lower is the disagreement or
One of the reasons direct methods was originally developed for analyzing X-ray diffraction is because almost all X-ray diffraction is kinematical. While most electron diffraction is dynamical, which is more difficult to interpret, there are instances in which mostly kinematical scattering intensities can be measured. One specific example is ...