Electron Diffraction Database

Crystallographic data on more than 170,000 crystalline materials. FDD (Electron Diffraction Database) with crystallographic data on more than 71,000 crystalline materials. PC-PDF (Powder Diffraction File) on CD-ROM for PCs. 

Widely used treatises and monographs on the theory and the applications of MRR-spectroscopy are available [8-//], also comprehensive reviews on all aspects of obtaining molecular structure from MRR-spectra [6,12,13], including rovib interactions [14] and the reliability of the results [15-17], Molecular structural and other data obtained from MRR spectroscopy have been compiled over the past decades [18,19], The most recent compilation is MOGADOC (short for Molecular Gas Phase Documentation ), a computerized database and retrieval system that is updated periodically and today contains more than 20,000 references, which were critically selected and evaluated by means of keywords. Included is work done by MRR-spectroscopy, electron diffraction of gases, and molecular radio astronomy the documentation refers to more than 6000 compounds. As an additional feature, MOGADOC contains explicit numerical data on the structure of approximately 2000 compounds. A detailed description can be found in ref. [20],... 

References to molecular structure and energies as derived from spectroscopy, electron diffraction and X-ray diffraction and theoretical calculation are included. They are indexed by compound, but the numerical data are not included. These references form the basis for the work on statistical-mechanical calculations of ideal-gas functions. References to publications on theoretical calculations and correlations, molecular dynamics, equations of state, compilations, error analysis and experimental techniques are also included and can be searched by topic area. It is possible to extract from the database recent publications containing experimental data selected on the basis of the properties measured. 

Today, of the order of 2000 surface structures are quantitatively known as retrieved by different surface-structure sensitive techniques, whereby those mostly used include LEED (Chapter 3.2.1), photo-electron diffraction (FED) (Chapter 3.2.2), specialized versions of X-ray diffraction (XRD) (Chapter 3.4.2), near-edge X-ray absorption fine structure (NEXAES) (Chapter 3.4.1), and ion scattering (IS) (Chapter 3.3). The structures solved up to 2003 are cataloged in the Surface Structure Database published by the National Institute of Standards and Technology (NIST-SSD) [1]. This electronic cataloge also provides a program to draw structural models, which has been used in this chapter. 

The identification of the superconducting phase YBagCug-O7 g provides an example in which knowledge of thermodynamics, i.e. the Gibbs phase rule and the theory of equilibrium phase diagrams coupled with X-ray diffraction techniques led to success. Further, the use of databases that can now be easily accessed and searched on-line provided leads to a preliminary structure determination. The procedures outlined here are among the basic approaches used in solid state chemistry research, but by no means are they the only ones. Clearly the results from other analytical techniques such as electron microscopy and diffraction, thermal... 

From the analysis of the data in the LIPID AT database (41), more than 150 different methods and method modifications have been used to collect data related to the lipid phase transitions. Almost 90% of the data is accounted for by less than 10 methods. Differential scaiming calorimetry strongly dominates the field with two thirds of all phase transition records. From the other experimental techniques, various fluorescent methods account for 10% of the information records. X-ray diffraction, nuclear magnetic resonance (NMR), Raman spectroscopy, electron spin resonance (ESR), infrared (IR) spectroscopy, and polarizing microscopy each contribute to about or less than 2-3% of the phase transition data records in the database. Especially useful in gaining insight into the mechanism and kinetics of lipid phase transitions has been time-resolved synchrotron X-ray diffraction (62,78-81). 

The Protein Data Bank (PDB) was established as a service to international science at the Brookhaven National Laboratory in the United States in 1971 to store and curate the atomic coordinates of macromo-lecular stmctures. Original versions of the whole data bank were distributed on magnetic tape to scientists, then on compact discs, and now they are freely available via the Internet (http //www.rcsb.org/). The PDB is part of the wwPDB whose mission is to ensure that the PDB archive remains an international resource with uniformly coded data. Other related sites are located in Japan (PDBj, http //www.pdbj.org/) and in Europe (MSD-EBI, http //www.ebi.ac.uk/msd/). In addition to coordinates, the PDB stores experimental diffraction data, and it provides many tools for analyzing and displaying structures. As of April 15, 2008, the PDB held 50,277 sets of atomic coordinates from proteins, nucleic acids, and carbohydrates determined by X-ray diffraction, NMR spectroscopy, and electron microscopy. About 5000 new stmctures are released each year, and the database is expected to treble to 150,000 by 2014. 

Raman microspectroscopy is the fastest and most powerful tool for analysis of phase transformations in contact loading. It can additionally provide information on residual stresses and/or chemical changes in the surface layers. However, limited databases of Raman spectra and difficulties with the interpretation of Raman spectra, as well as low accuracy of existing predictive tools for calculations of Raman spectra of solids, make it necessary to complement Raman data with electron or X-ray diffraction studies. Fourier-transform infrared microspectroscopy is another technique that can provide useful information on structural and compositional changes in the surface layer. 

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