Single-crystal structure of vanadium-doped La2Mo2O9

A high-precision X-ray diffraction study of single crystals of two compositions—La₂Mo_1.78V_0.22O_8.89 and La₂Mo_1.64V_0.36O_8.82—was performed. In the vanadium-doped compounds, as in the structure of the metastable β_ms phase of pure La₂Mo₂O₉, the La and Mo atoms and one of the three oxygen atoms are displaced from the threefold axis, on which they are located in the high-temperature β phase. The structure contains two partially occupied oxygen sites. It was shown that molybdenum atoms are partially replaced by vanadium atoms, which are not involved in the disordering, are located on the threefold axis, and are shifted toward one of the oxygen atoms. This is consistent with the temperature-induced changes in the structure of La₂Mo₂O₉ and the changes in the properties of these crystals caused by the introduction of vanadium atoms into the structure.