A powder diffraction study of iron oxide hydroxide nitrate, Fe2O(OH)(3)NO3center dot H2O: ab initio structure determination and anion exchange reactions

The structure of basic iron nitrate has been solved ab initio from X-ray po wder diffraction data collected with a conventional X-ray source. The symme try is monoclinic (Pc) with the cell parameters a = 3.0844(6) Angstrom, b 9 .508(2) Angstrom, c = 9.993(3) Angstrom, beta 91.01(2)degrees. The atom pos itions have been determined by the direct methods and the structure refined by the Rietveld method (R-F = 0.05). The final structure model is consiste nt with an oxide hydroxide nitrate chemical formula, Fe2O(OH)(3)NO3. H2O. T he structure consists of corrugated layers built from six-fold coordinated iron polyhedra sharing alternately edges and corners. The nitrate groups ar e intercalated between the layers. These groups can be exchanged by anions such as Cl, Br, MnO4 and OCOCH3. Exchange properties and thermal behaviour of exchanged products are discussed.