Structural refinements of high-pressure phases in germanium dioxide.

Recently, there has been substantial interest in the new high-pressure polymorphs of GeO2 synthesized in the laboratory. Previous investigators reported the synthesis of 'CaCl2-type', 'alpha-PbO2-type' and 'pyrite-type (modified-fluorite-type)' GeO2 at pressures of 30-130 GPa in laser-heated diamond anvil cells. In order to provide definitive information about the new high-pressure polymorphs, we performed Rietveld refinements of the structures. The structure refinements confirm that two of these high-pressure phases do have the alpha-PbO2-type and pyrite-type (modified-fluorite-type) structures.