EXAFS and Molecular Dynamics combined study of CaO-FeO-2SiO(2) glass. New insight into site significance in silicate glasses

A new and coherent view of the local environment of Fe2+ in silicate glasse s is derived from a combined study by EXAFS and Molecular Dynamics simulati on. Iron is located in distorted sites, whose geometry varies continuously from a tetrahedron to a triangular bipyramid. Iron polyhedra are apex-conne cted to the silicate network, while edge-linked to each other, matching wit h a random distribution of iron in the glass. Fe2+ does not have the signif icance of a network-forming element. Its local structure results from the f reezing of dynamical exchange processes occurring in the liquid.