X-Ray Diffraction Studies of Molten Salts

X-rays are diffracted from the electron shells of the individual ions making up the sample. The atomic scattering intensity a q) of each kind of atom in the sample 

Generally, the cation-anion distances in the melt are commensurate with the sum of their ionic radii or are slightly lower, but they are some 15 % smaller than the corresponding distance in the expanded crystal at the melting point. Notable exceptions to this in Table 3.4 are ZnBr2 and CdCL, with considerably smaller 

Ri values than their r+ + r, for which incomplete ionization and a partial covalent bonding are responsible. 

In the case of x-ray diffraction involving molten salts with polyatomic anions (nitrate, carbonate, sulfate) [69, 70] the information is obscured by the intra-anionic distances (central atom to oxygen) and little useful information on the stmcture of the melt is obtained. The same problem occurs with alkali metal thiocyanates [78], where the data confirm the structure of the linear SCN anion but does not position the cations with respect to it. 

---