Revealing the local structure of CuMo$_{1-x}$W$_x$O$_4$ solid solutions by multi-edge X-ray absorption spectroscopy

TL;DR

This study uses multi-edge X-ray absorption spectroscopy and reverse Monte Carlo analysis to investigate how tungsten substitution affects the local structure of CuMo$_{1-x}$W$_x$O$_4$ solid solutions, revealing tungsten's dominant role in structure.

Contribution

It introduces a multi-edge EXAFS analysis combined with reverse Monte Carlo modeling to elucidate local structural changes in CuMo$_{1-x}$W$_x$O$_4$ solid solutions due to tungsten substitution.

Findings

Tungsten-related sublattice primarily determines the structure.

Molybdenum atoms adapt to distorted environments.

Coordination remains octahedral across compositions.

Abstract

The effect of tungsten substitution with molybdenum on the structure of CuMo$_{1-x}$W$_x$O$_4$ ($x$ = 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 L$_3$-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) $f(\varphi)$. 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 CuWO$_4$ for all the studied compositions.