Search hints and tips
The COD offers 2 powerful options for a search :
  1. By combining in the way you choose : text (2 words or parts of words), elements (1 to 8, with formula numbers or not), volume (min and max), and strict number of elements.

  2. There is no obligation for filling all boxes, of course. Select those corresponding to your needs (see below).

    - Text search is on mineral name if any, author(s) if any, reference including publication title, journal name, journal volume, journal pages). You can perform the search with one word or with  word1 AND word2 (ex : word1 = amphibole AND word2 = 1999 - but if there are pages numbered 1999, they will be shown - ; or use part of words ex : miner, etc). Entries which contained nothing as text part can be found by using 'unknown' as a keyword. You may also directly ask the database by sending requests like :

    - Selecting elements (up to 8), allows for an inclusive search (compounds with other elements are not excluded). 
    NOTE :  Apply the following rules : Typing Ba and N may return compounds containing Ba and Ni, In, Sn, Zn ! For one-letter elements like N (O, P, S, V, etc), type a space before the element and also after it and the search should work better. 

    It is also possible to search by formula in a special way : an element should be followed by a space (and preceded also by a space if that element has only one letter) and then the number of elements : C 5. Some formula may be complex like in the superconductors : O 6.9 should work too ! Obtaining Al2O3 will be done also by using two boxes, one  with Al 2 and the other with O 3 (one space between the element and the number).

    - Volume range between Vmin and Vmax. This can be very efficient if combined with elements for finding if your own compound structure is already in the database (or an isostructural one).

    - Strict number of elements. Giving elements combined with the number of elements allows for a strict search and the easy finding of binary, ternary compounds, etc (ex : elements Al and O with n = 2 elements should give Al2O3, if it is inside of the COD). Typing only n = 2 or n = 3 (etc) will result in the whole list of binary and ternary compounds (if < 300). Typing n > 1 with only one element Xy will return compounds with n elements having at least Xy as element, etc. 

  3. By cell parameters ranges amin-amax, bmin-bmax etc. This is clear enough.
Given that the COD was built mainly for verifying if, knowing your sample cell, you are not redetermining an already known structure, these above search possibilities should fulfill your needs (especially option 2 and using volume ranges, requiring the cell knowledge). 

Warning : some entries (from the AMCSD) are not containing the formula but only the list of elements (was not trivial to estimate the formula from the space group and the atomic coordinates). There are also some problems when elements having only one character were described with a letter as second character (Oa, Ob, Oc, Od, Oh, Wa, etc) in the list of atomic coordinates. 

About CIFs : see the IUCr Web page. Remember that a CIF may contain several crystal data. Your entry may well be inside of a CIF containing up to 100 entries. Once downloaded, edit the CIF (by a text editor) and search for your entry if it is a multiple CIF. See the advice to potential CIF donators. New CIF software : EnCIFer by CCDC.

The CIF filenames in the COD :
- from 1000000.cif to 1999999.cif : files uploaded by crystallographers or donated by laboratories. 
- from 9000000.cif to 9999999.cif : files donated by the American Mineralogist Crystal Structure Database.
There is place for 9.000.000 CIFs in the COD !

Best wishes !
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Crystallography Open Database
Updated 2016-01-07