High-pressure structures of alpha- and delta-ZrMo2O8

In situ high-pressure synchrotron X-ray powder diffraction studies of trigonal alpha-ZrMo(2)O(8), zirconium molybdate, have been performed from ambient conditions to 1.9 GPa, over the alpha-delta phase transition at 1.06-1.11 GPa. The monoclinic structure of delta-ZrMo(2)O(8), stable between 1.1 and 2.5 GPa at 298 K, has been solved by direct methods and refined using the Rietveld method. Significant distortions of the ZrO(6) and MoO(4) polyhedral elements are observed for delta-ZrMo(2)O(8), as compared to the ambient conditions of the alpha-phase, while the packing of anions becomes more symmetric at high pressure.