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The International Centre for Diffraction Data (ICDD) maintains a database of powder diffraction patterns, the Powder Diffraction File (PDF), including the d-spacings (related to angle of diffraction) and relative intensities of observable diffraction peaks.
Reflection positions and intensities of known crystal phases, mostly from X-ray diffraction data, are stored, as d-I data pairs, in the Powder Diffraction File database. The list of d-I data pairs is highly characteristic of a crystal phase and, thus, suitable for the identification, also called ‘fingerprinting’, of crystal phases.
This is directly related to the fact that information is lost by the collapse of the 3D space onto a 1D axis. Nevertheless, powder X-ray diffraction is a powerful and useful technique in its own right. It is mostly used to characterize and identify phases, and to refine details of an already known structure, rather than solving unknown structures.
The Cambridge Structural Database (CSD) is both a repository and a validated and curated resource for the three-dimensional structural data of molecules generally containing at least carbon and hydrogen, comprising a wide range of organic, metal-organic and organometallic molecules.
The Crystallography Open Database (COD) is a database of crystal structures. [1] Unlike similar crystallographic databases , the database is entirely open-access, with registered users able to contribute published and unpublished structures of small molecules and small to medium-sized unit cell crystals to the database.
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Typically, powder X-ray diffraction (XRD) is an average of randomly oriented microcrystals that should equally represent all crystal orientation if a large enough sample is present. X-rays are directed at the sample while slowly rotated that produce a diffraction pattern that shows intensity of x-rays collected at different angles. Randomly ...
The front entrance of CCDC headquarters in Cambridge, UK. The Cambridge Crystallographic Data Centre (CCDC) is a non-profit organisation based in Cambridge, England.Its primary [citation needed] activity is the compilation and maintenance of the Cambridge Structural Database, a database of small molecule crystal structures.