Search Crystal Data

Currently, there are about 197,500 entries in the National Institute of Standards and Technology (NIST) Crystal Data File. An exhaustive search takes about one minute. Unit cell parameters are very definitive. Usually only one or a few hits are found and the appropriate Hterature reference(s) are Hsted. If no hits are found, the stmcture has not been previously reported. 

Indexings and Lattice Parameter Determination. From a powder pattern of a single component it is possible to determine the indices of many reflections. From this information and the 20-values for the reflections, it is possible to determine the unit cell parameters. As with single crystals this information can then be used to identify the material by searching the NIST Crystal Data File (see "SmaU Molecule Single Stmcture Determination" above). 

Because the 3D-structure of the receptor was not yet known, we wanted to derive a pharmacophore model, to prove this hypothesis. Most of the H2-antagonists have much conformational freedom. Evaluation of available crystal data and a systematic conformational search revealed mainly bent conformations,... 

E. X-ray Crystal Data Search System. The National Bureau of Standards (NBS) has collected a file of data pertaining to some 24,000 crystals, including those in the Cambridge file described above (20). The data in the NBS file include the cell parameters, the number of molecules. Z. in the unit cell, the measured and calculated densities of the crystal and two determinative ratios, such as A/B and A/C. Every com-... 

The crystal used for data coUection was transferred to an Enraf-Nonius CAD-4 diffractometer. Automatic peak search and indexing procedures yielded the same monoclinic cell as derived from the X-ray powder diffraction data and precession photographs. Testing showed that the cell was indeed primitive and that there was no superlattice present. Table 5 gives the crystal data and X-ray experimental parameters, and Table 6, the interatomic distances and angles. Positional and thermal parameters are given in Table S3 (Supporting Information)... 

For example, two comprehensive databases, ICSD and CSD, contain crystallographic data and structural information about inorganic, and organic and metal organic compounds, respectively, while NIST database encompasses all types of compounds but provides only crystal data with references. Other databases are dedicated to specific classes of materials, such as metals and alloys, proteins and macromolecules, minerals or zeolites. Search-match utilities are usually provided with databases or they may be obtained separately. 

Recently the ICDD Powder Diffraction File underwent a substantial and useful upgrade calculated patterns based on single crystal data from the ICSD file have been included into the PDF-2/PDF-4 Full File calculated patterns of structures stored in the CSD file, have been included into the PDF-4 Organics (see Table 4.3). These additions make it possible to conduct searches and find matches with computed digitized powder patterns in addition to experimentally measured powder diffraction data, thus improving automation, simplifying phase identification process and considerably expanding the applicability of the powder method for a qualitative phase analysis. 

The validation of the modelled structures has been achieved on comparing calculated and observed XRPD patterns, besides matching the calculated and experimental chemical compositions and crystal data, including the space group. To initiate a search for known crystal stmctures that show structural features comparable to those of the unknown structure, the latter data are already indispensable. 

ConQuest provides search, retrieval, and display facilities for the CSDJ Individual queries can be set up to interrogate the bibliographic, chemical text, and crystal data fields listed in Table 2, and, in particular, the program provides extensive graphical facilities for the definition of 2D and 3D substructure searches. The 2D searches interrogate the chemical connection tables alone, while... 

Table 14.6 Crystal structure generation by the Prom procedure for chlorocorannulene. Raw structures output of the first search first sorting clustered structures from raw structures (no optimization) final sorting number of optimized crystal structures best energy (kJ mol ) best lattice energy of final sorting. For some space gronps, results for the dicarbonyl derivative are also reported. Crystal data are collected in the Snpplementary material, file chlorcor.oeh and colcor.oeh...

Provost, A. Allegre, C. J. (1979). Process identification and search for optimal parameters from major-element data. General presentation with emphasis on the fractional crystallization process. Geochim. Cosmochim. Acta, 43, 487-501. 

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