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I'm currently downloading .cif files from various online databases and using openbabel to convert the fractional coordinates that are in the .cif files into .xyz files. The typical output will look something like this:

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Spinel \begin{array}{c|c c c} \ce{Mg} & 1.01054 & 1.01054 & 1.01054\\\hline \ce{Al} & 1.01054 & 1.01054 & 1.01054\\\hline \ce{Al} & 4.04217 & 4.04217 & 4.04217\\\hline \ce{Mg} & 4.04217 & 4.04217 & 4.04217\\\hline \ce{O} & 2.11390 & 2.11390 & 2.11390 \end{array} My problem is that I would like the ionic radii of each element, instead of their name. Does anyone know of a way to recover this information from the original CIF file or am I just stuck with looking up the radii manually on, https://en.wikipedia.org/wiki/Ionic_radius ?

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    – M.A.R.
    Jul 17, 2015 at 18:24
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    $\begingroup$ Well those numbers with decimals looked really eye-jarring with just a space separating them. $\endgroup$
    – M.A.R.
    Jul 17, 2015 at 18:31

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The CIF file won't contain information on atomic radii, only the positions (in fractional space).

Consider that the atom might be ionic, covalent, etc. so you'll have to choose the atomic radius definition you feel is most appropriate. (Or run some sort of quantum calculation and use the resulting [electron density to define an atomic radius].)

For what it's worth, Open Babel does have a data table of covalent and van der Waals atomic radii, but it sounds like you want something else.

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