Evidence for symmetric cationic sites in zirconium-bearing oxide glasses

Abstract

The local environment of Zr in a borosilicate glass has been investigated by combining molecular dynamics (MD) simulations with Zr $K$-edge x-ray absorption spectroscopy (XAS) measurements. Two- and three-body distribution functions in agreement with the experimental data were obtained. The oxygen first neighbors around Zr are found to be narrowly distributed, revealing almost perfectly regular $\mathrm{Zr}{\mathrm{O}}_{6}$ octahedra. Significant three-body contributions (Zr-O-O) to the XAS signal are observed, probing the existence of highly symmetric cationic sites in a glassy network. The ${g}_{\mathrm{Zr}\mathrm{O}}(r)$ first peak derived from the experimental data is narrower than the one given by the MD model, thus providing elements for further improvements of the MD potentials.