Pressure-induced phase transitions in CdMoO4: An in-situ high pressure X-ray diffraction study up to 52 GPa

An in-situ high pressure X-ray diffraction study on CdMoO4 has been carried out in the diamond anvil cell up to 52 GPa at room temperature. From the high pressure diffraction data we find two pressure-induced phase transitions, one near 12 GPa and another near 25 GPa. The first transition is from scheelite (tetragonal) to wolframite-type structure (monoclinic) and the second transition is also to a monoclinic lattice, related to the BaWO4-II structure. There is no significant change in the molar volume at the first transition, while at the second transition the volume decreases by about similar to 12%. We conclude that the latter is due to change in the Mo-O coordination to truly octahedral coordination. The above results are consistent with the conclusions of a recent high pressure Raman study.