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The crystal structures of some nickel hexacyanoferrates (II, III), including mixed compositions containing Na + , K + and Cs + , were resolved and refined from XRD powder patterns. Data from infrared, Mössbauer and adsorption techniques provided complementary structural information. The crystal structures of Ni 3 Fe(CN) 6 2 ⋅16H 2 O and NiCs 2 Fe(CN) 6 were refined in space group Fm3m. NiNa 2 Fe(CN) 6 ⋅2H 2 O and NiK 2 Fe(CN) 6 ⋅2H 2 O were found to be orthorhombic (space group Pmn2 1 ). This structure (Pmn2 1 ) results from a distortion around the alkali ion, which appears as a monohydrated interstitial species. On ionic exchange in an aqueous solution containing Cs + , the orthorhombic distortion disappears and the cubic cell is obtained. Cs + is a large cation and space is not available for interstitial water molecules. This orthorhombic model is also supported by the Mössbauer spectra of the ferrous analogs, FeK 2 Fe(CN) 6 ⋅xH 2 O and FePt(CN) 6 . © 2004 International Centre for Diffraction Data.
Martı́nez-Garcı́a et al. (2004) studied this question.