Crystal structure of the metastable cubic βms phase of La2Mo2O9 single crystal at T = 33 K

Abstract

The structure of the cubic metastable βms phase of La2Mo2O9 single crystal has been precisely investigated by X-ray diffraction at 33 K for the first time. The measurement of the unit-cell parameter of this crystal in the range from room temperature to 33 K showed that the unit-cell parameter and volume change continuously in this range. The crystal has a similar structure at T = 33 K and at room temperature. A local lowering of the symmetry for La and Mo atoms, caused by their displacement, is confirmed, and a similar displacement (which was not observed at room temperature) is revealed for O(1) atoms. The thermal parameters for O(2) and O(3) atoms do not change with a decrease in temperature, in contrast to the thermal parameters of Mo, La, and O(1) atoms. This fact indicates that the O(2) and O3 atoms in this crystal are statically disordered.