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

Abstract

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 ∼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.