Revealing the local structure of CuMo1−xWxO4 solid solutions by multi-edge X-ray absorption spectroscopy

The effect of tungsten substitution with molybdenum on the structure of CuMo_1−xW_xO₄ (x=0.20, 0.30, 0.50, 0.75) solid solutions was studied by multi-edge X-ray absorption spectroscopy. The simultaneous analysis of EXAFS spectra measured at several (Cu K-edge, Mo K-edge and W L₃-edge) absorption edges was performed by the reverse Monte Carlo method taking into account multiple-scattering effects. The degree of distortion of the coordination shells and its dependence on the composition were estimated from partial radial distribution functions (RDFs) g(r) and bond angle distribution functions (BADFs) f(φ). The analysis of partial RDFs suggests that the structure of solid solutions is mainly determined by the tungsten-related sublattice, while molybdenum atoms adapt to a locally distorted environment. As a result, the coordination of both tungsten and molybdenum atoms remains octahedral as in CuWO₄ for all the studied compositions.