On the crystal structures of some nickel hexacyanoferrates (II,III).

RICARDO MARTÍNEZ GARCÍA; E. REGUERA RUIZ; J. BALMASEDA

POWDER DIFFRACTION

J C P D S-INT CENTRE DIFFRACTION DATA

Año: 2004 vol. 19 p. 284 - 291

0885-7156

The crystal structures of some nickel hexacyanoferrates ~II, III!, including mixed compositions containing Na1, K1 and Cs1, were resolved and refined from XRD powder patterns. Data from infrared, Mo¨ssbauer and adsorption techniques provided complementary structural information. The crystal structures of Ni3(Fe(CN)6)2?·16H2O and NiCs2(Fe(CN)6) were refined in space group Fm3m. NiNa2(Fe(CN)6)·2H2O and NiK2(Fe(CN)6)·2H2O were found to be orthorhombic (space group Pmn21). This structure (Pmn21) results from a distortion around the alkali ion, which appears as a monohydrated interstitial species. On ionic exchange in an aqueous solution containing Cs1, the orthorhombic distortion disappears and the cubic cell is obtained. Cs1 is a large cation and space is not available for interstitial water molecules. This orthorhombic model is also supported by the Mo¨ssbauer spectra of the ferrous analogs, FeK2(Fe(CN)6)·xH2O and Fe(Pt(CN)6).