Evaluation of ferrous and ferric Mössbauer fractions, part II

Mossbauer fractions f are reported for various ferrous- and,or ferric-containing oxides, hydroxides, silicates, and phosphates to extend the list previously reported by De Grave and Van Alboom (1991). The f fractions were evaluated from the experimental temperature dependencies of their center shifts, assuming the Debye model for the lattice vibrations. For most Fe2+ sites the characteristic Mossbauer or lattice temperatures Theta(M) are in the range 300-400 K, while those for Fe3+ sites are close to or exceed 500 K, implying significantly higher f fractions for Fe3+ than for Fe2+, in particular at room temperature. A correlation between OM and the coordination type, or, for a given valence state and coordination type, between OM and the mineral type is, however, not obvious