I want to know how to confirm the cation and anion of any crystalline material from CIF file? What is the key idea behind this analysis.
A little more specifics would be helpful. Do you want to experimentally verify the site occupations for the compound described by the cif? Do a plausibility check on the structure described in the cif? Or do you need to know how cations and anions are encoded in a cif-file?
Mr. Dasadia,
If you have only CIF, you can only assume, analysing for yourself (not confirm) the cations and the anions, in given crystals of zwitterions on the base of CIF using the progma PLATON. It is free, internet available software. Than you should analyse the Fourier-density map. Especially the H-positions in the acids, and those of the cations in the bases.
The unambigouse confirmation, however, you can obtain, only if you have the crystallographic hkl-intensities (i.e. the initial data collected set) and perform analysis (independent solutions) of the crystal structure, optimitzing by least square method. Depending of the R-factor at the variety of H-positions, it is enable to determine the type of the interacting species in the crystals.
While I agree with Bojidarka Ivanova that X-ray diffraction data are necessary for an unambiguous answer to your question, it's worth pointing out that for simple binary crystal structures, electronegativities may provide a rough estimate. In general, the more electronegative atom will attract electrons and become the anion, while the less electronegative atom will give up its valence electrons and become the cation.
It is becoming increasingly harder to understand the questions here. The only interpretation I can give is that the guy want to know how to tell if an atom in a given position should be considered in oxidation state zero or in another.in that case chemistry and bonding can help. However please people double check your questions and try to follow those you place...
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