Probing the Thermochromic Phase Transition in CuMoO₄ by EXAFS Spectroscopy

Extended X-ray absorption fine structure (EXAFS) spectroscopy at the Mo K-edge is used to follow the thermochromic γ-to-α phase transition in copper molybdate (CuMoO₄). The temperature dependence (10–300 K) of the radial distribution function (RDF) for the Mo–O atom pairs in the first coordination shell of molybdenum atoms is reconstructed by the regularization-like method from the experimental EXAFS spectra. The analysis of the RDFs suggests that the transition occurs gradually within the two-phase coexistence range of 225–275 K. The local environment of molybdenum atoms transforms upon the γ-to-α phase transition from strongly distorted octahedral to less distorted tetrahedral coordination.