Anomalous X-ray Scattering Study of Local Structures in the Superionic Conducting Glass (CuI)_0.3(Cu₂O)_0.35(MoO₃)_0.35

The anomalous X-ray scattering (AXS) method using Cu and Mo K absorption edges has been employed for obtaining the local structural information of superionic conducting glass having the composition (CuI)_0.3(Cu₂O)_0.35(MoO₃)_0.35. The possible atomic arrangements in near-neighbor region of this glass were estimated by coupling the results with the least-squares analysis so as to reproduce two differential intensity profiles for Cu and Mo as well as the ordinary scattering profile. The coordination number of oxygen around Mo is found to be 6.1 at the distance of 0.187 nm. This implies that the MoO₆ octahedral unit is a more probable structural entity in the glass rather than MoO₄ tetrahedra which has been proposed based on infrared spectroscopy. The pre-peak shoulder observed at about 10 nm⁻¹ may be attributed to density fluctuation originating from the MoO₆ octahedral units connected with the corner sharing linkage, in which the correlation length is about 0.8 nm. The value of the coordination number of I⁻ around Cu⁺ is estimated as 4.3 at 0.261 nm, suggesting an arrangement similar to that in molten CuI.