Structural Investigations under High Pressure

Abstract

The high pressure structures of AX₂ compounds have been refined in situ up to 60 GPa in a diamond anvil cell with an imaging plate in the angle dispersive mode using a low power laboratory x-ray tube and/ or synchrotron radiation. Results for GeO₂ obtained using both sources are compared. Under the same conditions (pressure, hydrostaticity, completion of phase transformations), the refinements by the Rietveld method yielded identical atomic positions and cell parameters. A structure map of the AX₂ compounds as a function of the coordination number has been established. The transition pathways depend on the filling of the d orbitals.