Local coordination geometry around Cu+ and Cu2+ ions in silicate glasses: an X-ray absorption near edge structure investigation

We present an X-ray absorption near edge structure (XANES) study on Cu+ and Cu2+ ions in silicate glasses at the Cu K-edge, aimed to determine the geometry of the local structure around the metal. This study is based on the comparison between experimental data and theoretical calculations made in the framework of multiple scattering theory. The XANES signals relative to several clusters are simulated on the basis of known crystalline structures involving Cu+ and Cu2+ ions in silicate matrices. Concerning the Cu2+ ill glass, the simulations suggest the presence of a square coordination of oxygen atoms around the absorber, with a possible presence of metal ions in the second shell. As for the Cu+ ions, the metal clustering is excluded and a linear O-Cu-O coordination is evidenced.