Pressure induced amorphization of ZrMo ₂O ₈ and its relaxation on decompression as seen by in situ total x-ray scattering

The pressure induced amorphization of the negative thermal expansion material cubic ZrMo ₂O ₈ was examined in situ within a diamond anvil cell, using high energy x-ray total scattering, during compression up to ∼7.2 GPa, and then decompressed. The amorphization upon compression was largely complete by ∼3 GPa. There was significant, but not complete, structural relaxation of the amorphous material on decompression; the pair distribution function (PDF) for the material recovered from 7.2 GPa closely resembled that for the sample during initial compression at ∼5.5 GPa. The PDFs indicated that the amorphization, densification, and relaxation of the amorphous solid involve changes in the first coordination shell of molybdenum and the creation/loss of Mo-O-M bridges with ∼3.4 Å Mo-M separation (M-Mo or Zr).