High-pressure structures of alpha- and delta-ZrMo2O8

In situ high-pressure synchrotron X-ray powder diffraction studies of trigo nal alpha -ZrMo2O8, zirconium molybdate, have been performed from ambient c onditions to 1.9 GPa, over the alpha-delta phase transition at 1.06-1.11 GP a. The monoclinic structure of delta -ZrMo2O8, stable between 1.1 and 2.5 G Pa at 298 K, has been solved by direct methods and refined using the Rietve ld method. Significant distortions of the ZrO6 and MoO4 polyhedral elements are observed for delta -ZrMo2O8, as compared to the ambient conditions of the alpha -phase, while the packing of anions becomes more symmetric at hig h pressure.