The Mössbauer spectra of hydroxycarbonate green rusts

Abstract

Mössbauer spectra of Fe²⁺Fe³⁺ and Fe²⁺Al hydroxycarbonates taken in the paramagnetic state were fitted using two Fe²⁺ and Fe³⁺ doublets each. These spectra can be interpreted in terms of an ordered cation arrangement in the pyroaurite-type structure. The inner Fe²⁺ doublet seems to be the outcome of excess Fe³⁺ in the samples studied. The outer Fe²⁺ doublet (quadrupole splitting ∼2·8 mm s⁻¹, FWHM = 0·26 mm s⁻¹) is relatively well-defined and can, together with the fact that this doublet disappears on oxidation, possibly serve to identify these compounds in natural systems.