Polyamorphism in network structures

Abstract

Reports of high-density amorphous forms of ice, quartz and Si have intensified the search for amorphous polymorphs in other systems. The network structures that exhibit pressure-induced amorphization are interesting from the point of view of polyamorphism. Recent in-situ high pressure Raman scattering and synchrotron x-ray diffraction studies on negative thermal expansion material zirconium tungstate have revealed an amorphous to amorphous transition at 19 GPa. The transition was identified for the discontinuities in the structural parameters such as position and height of the first peak of the structure factor and that in the tungstate internal vibrational mode frequency. Another compound, vanadium pentaoxide that forms a glass during melt-quenching, is also found to turn amorphous at 40 GPa, pointing to a possibility of polyamorphism.