When I google there are multiple download links from different sources, I just want to know a standard database that crystallographers use. Thanks
First a declaration of interest: I work for the Cambridge Crystallographic Data Centre who produce the Cambridge Structural Database.
There are indeed several sources for crystallography data: Historically, the official depositories are the Protein Data Bank for protein crystallography, the Cambridge Structural Database (CSD) for small molecule organic and organometallic crystallography and the Inorganic Crystal Structure Database for inorganic structures. The latter division is down to carbon atoms: if the small molecules you are interested in contain carbon, then look in the CSD; if not you need the ICSD
The CCDC sells the full CSD system, heavily discounted for academic users, but provides free access to individual crystal structures through the data request form on the CCDC web site; if you have a specific reference that you want to get the data on then that's the path to use (http://www.ccdc.cam.ac.uk)
I have to chip in the free alternative here: the crystallography open database, COD (http://www.crystallography.net). The coverage of specific areas might not always be as good as the commercial options (yet), but the quality of the content is at least no worse than ICSD, from what I have seen. Some outdated structures exist, but that problem is in all the databases, since they all store also "legacy" (read "wrong") structures from very old studies.
On the CIF technical side, I have had more problems with parsing ICSD than with parsing COD, meaning that the CIF's themselves generally are of high quality (I have parsed the whole databases for testing the stability of my own code).
Thanks all for the nice responses. After briefly browsing and doing some search on the few sites mentioned above, I have to say Torbjorn's suggestion COD has the best interface and very comprehensive results (although I am sure some of the early 1900s ones are probably "legacy/wrong"). Again, thank you all for helping, I've rated all of you up.
COD is large, good and free... ICSD could be, somehow, a bad and a break in experimental development. All modern XRD software is linked, through Internet, to some ICSD crystallographyc files (CIF), obtained, calculated by ancestors...
Some young researchers don't even realise that the experimental data they eventualy report, using that technology, is just a "read/upload" from ICSD database... Shamely, there is no further refinament on cell parameters or on Wyckoff positions...
PS
I don'd blame ICSD, not at all... It's a wonderfull and large database, working on some "standardization", well integrated in hardware... I can never presume that is a bad intended database... but I think it has more to work in letting human thinking, decisioning, dreaming... It may be good an advertisement: go on, we gave just a good start, eventually...
I would suggest http://www.crystallography.net/
An open-access collection of crystal structures of organic, inorganic, metal-organic compounds and minerals, excluding biopolymers
I hope, MATCH will help you.
http://www.crystalimpact.com/match/match18.htm
from here you may download a recent COD snapshot in DataWarrior format from which you can export SD-files and SMILES, if you need to:
http://www.openmolecules.org/datawarrior/datafiles.html
COD is one of the best place to download the cif files.
http://www.crystallography.net/cod/search.html
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