Encyclopedia of Crystallographic Prototypes

Information about a crystal's structure, including the space group, lattice constants, composition, and occupied Wyckoff positions, including coordinates, are stored in an Crystallographic Information File, universally abbreviated as CIF. The CIF format was developed by the International Union of Crystallography (IUCr) and released in 1991.

Each structure in the Encyclopedia has its own CIF, based on the published data about the structure. We use a minimal CIF, containing the minimum information needed to reconstruct the crystal. Other sites may include information about the experimental conditions, bonding information, thermal atomic displacements of the atoms in the crystal, and much more. It is even possible to publish a scientific paper inside a CIF.

There are many sources for these verbose CIFs. We give several examples here:

The Original Publication

Authors often include a CIF, or the information needed to create a CIF, in their paper or in the supplementary information published with the paper. Most entries in the Encyclopedia are associated with a published paper, and the reference section for that structure will have a link to the paper's Digital Object Identifier (DOI), if available. Clicking on that link will take you to its online web page.

Inorganic Crystal Structure Database (ICSD)

FIZ Karlsruhe maintains the Inorganic Crystal Structure Database (ICSD), a compilation of completely identified crystal structures, both experimental and theoretical, submitted by researchers from throughout the world. Each entry in the ICSD has a unique index number, we list on our structure web pages. Unfortunately the CIF associated with this number is behind a paywall, but clicking on the ICSD number will take you to a page where you can download the CIF provided by the CCDC. There are daily limits on the number of downloads.

Cambridge Structural Database (CSD)

The Cambridge Structural Database (CSD) is similar to the ICSD but focuses on small molecule organic and metal-organic crystal structures. Like the ICSD, its information is behind a paywall. Again like the ICSD, clicking on the CCDC number will take you to a page where you can download the CIF provided by the CCDC. There are daily limits on the number of downloads. One caveat, if the CCDC number is the same as an ICSD number, you will see both structures. It should not be too difficult to determine which is the one you want.

Cambridge Crystallographic Data Centre (CCDC)

Cambridge Crystallographic Data Centre (CCDC) maintains the CSD and links to the ICSD. Each entry in the CCDC has a unique index number, and these entries can be accessed via the CCDC search page using the CCDC or ICSD index or the publication DOI. The CIF provided by the CCDC is not as complete as the underlying ICSD or the CSD entry, but it does provide enough information to reconstruct the crystal. The service is free, but only a limited number of CIF downloads are available on a given day.

Other sites include three which we often use as a resource to locate the original articles describing a structure. All provide at least basic CIFs for each structure.

American Mineralogist Crystal Structure Database (AMCSD)

The open source American Mineralogist Crystal Structure Database (AMCSD) gives the structural data for a variety of minerals published in multiple journals.

Materials Project

The open source Materials Project contains hundreds of thousands of computational structures for many materials. It references the original experimental publication, when available.

Springer Materials

Springer Materials maintains a database of crystal structures searchable by composition and including phase diagrams. Unfortunately it is often difficult to search through all the entries and find the actual crystal structure, and that structure is behind a paywall.