Experimental and theoretical investigation of ThGeO[subscript 4] at high pressure
We report here the combined results of angle-dispersive x-ray diffraction experiments performed on ThGeO{sub 4} up to 40 GPa and total-energy density-functional theory calculations. Zircon-type ThGeO{sub 4} is found to undergo a pressure-driven phase transition at 11 GPa to the tetragonal scheelite structure. A second phase transition to a monoclinic M-fergusonite type is found beyond 26 GPa. The same transition has been observed in samples that crystallize in the scheelite phase at ambient pressure. No additional phase transition or evidence of decomposition of ThGeO{sub 4} has been detected up to 40 GPa. The unit-cell parameters of the monoclinic high-pressure phase are a = 4.98(2) {angstrom}, b = 11.08(4) {angstrom}, c = 4.87(2) {angstrom}, and {beta} = 90.1(1), Z = 4 at 28.8 GPa. The scheelite-fergusonite transition is reversible and the zircon-scheelite transition nonreversible. From the experiments and the calculations, the room-temperature equation of state for the different phases is also obtained. The anisotropic compressibility of the studied crystal is discussed in terms of the differential compressibility of the Th-O and Ge-O bonds.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 1005850
- Journal Information:
- Phys. Rev. B, Vol. 80, Issue (9) ; 2009; ISSN 1098-0121
- Country of Publication:
- United States
- Language:
- ENGLISH
Similar Records
Polymorphism in Strontium Tungstate SrWO4 under Quasi-Hydrostatic Compression
Pressure-induced structural transformations and new polymorphs in BiVO4