Environment of ferrous iron in CaFeSi2O6 glass; contributions of EXAFS and molecular dynamics

Local and medium-range environment of Fe in the totally reduced oxide glass CaFeSi2O6 are studied by combining EXAFS spectroscopy and molecular dynamics (MD) simulations. Ferrous Fe is located in sites with a distribution of Fe-O distances, with typical geometries close to a tetrahedron and to a triangular bipyramid. At medium-range order, the presence of Ca and Fe as next nearest neighbours is found in the experimental data and in the simulations. The Fe polyhedra are apex-connected to the silicate network, while edge-linked to each other and to Ca polyhedra. The occurrence frequency of these edge-sharing polyhedra is that expected for a random distribution or a limited segregation of Fe in the glass. 19 refs.