Computer-based searches

Allen FH, Bellard S, Brice MD, Cartwright BA, Doubleday A, Higgs H, Hummelink T, Hummelink-Peter BG, Kennard O, Motherwell WDS, Rodgers JR, Watson DG. The Cambridge Crystallographic Data Centre Computer-based search, retrieval, analysis and display of information. Acta Crystallogr, Sect B 1979 B35 2331-9. 

This review describes the current status of silenes (silaethylenes, silaethenes), molecules which contain a silicon-carbon double bond. The heart of the material is derived from a computer-based search of the literature which we believe reports all silenes that have been described to date, either as isolated species, chemically trapped species, proposed intermediates (in reactions where some experimental evidence has been provided), or as the result of molecular orbital calculations. Ionized species... 

Computer-Based Searches and Other Aids to the Literature... 

Hummelink-Peters, O. Kennard, W. D. S. Motherwell, J. R. Rodgers, and D. G. Watson, Acta Crystallogr., B35, 2331 (1979). The Cambridge Crystallographic Data Center Computer-Based Search, Retrieval, Analysis and Display of Information. 

Chemical Titles is a computer-produced list of titles of chemical papers arranged by keywords (KWIC, keyword in context), and produced by Chemical Abstracts Services. The titles appear so that the keywords are listed in the center of the column. It is based on the contents pages of some 700 journals abstracted in Chemical Abstracts, and appears twice monthly. For the most efficient use, a list of keywords is compiled, and the availability of this service on magnetic tape means that computer-based searches of these titles can be made. 

Allen, F. H.. Bellard, S., Brice, M. D., Cartwright, B. A., Doubleday, A., Higgs, H., Hummeliiik, T., Hummelink-Peters, B. G., Kennard, O., Motherwell, W D. S., Rodgers, J. R., and Watson, D. G. The Cambridge Crystallographic Data Centre computer-based search, retrieval, analysis and display of information Acta Cryst. B35, 2331-2339 (1979). 

Every crystalline phase in a sample has a unique powder diffraction pattern determined from the unit cell dimensions and the atomic arrangement within the unit cell. It can be considered a fingerprint of the material. Thus, powder diffraction can be used for phase identification by comparing measured data with diffraction diagrams from known phases. The most efficient computer searchable crystallographic database is the PDF-4 from the International Centre for Diffraction Data (ICDD) [3]. It is used by very efficient computer-based search-processes. In 2007 the PDF-4-i- database contains information about Bragg-positions and X-ray intensities for more than 450000 compounds, out of which there are about 107 500 data sets with atomic coordinates. New entries are added every year. The positions of the peaks in the measured pattern have to be determined. This can be done manually, but effective, fast and reliable automatic peak search methods have been developed. The method can obviously be successful only if the phases in the sample are included in the database. However, the database can also help to determine unknown phases if X-ray data exist for another isostructural compound albeit with a different composition. 

POLYMERS, ADDITIVES, SURFACTANTS AND THEIR MIXTURES COMPUTER-BASED SEARCH WITH SPECIAL FTIR LIBRARIES... 

As just noted, correlation charts seldom suffice for the positive identification of an organic compound from its IR spectrum. However, several catalogs of IR spectra are available that assist in qualitative identification by providing comparison spectra for a large number of pure compounds. Manually searching large catalogs of spectra is slow and tedious. For this reason, computer-based search systems are widely used. 

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