Experimental and theoretical investigation of ThGeO[subscript 4] at high pressure

Journal Article · Tue Sep 15 04:00:00 EDT 2009 · Phys. Rev. B

DOI:https://doi.org/10.1103/PhysRevB.80.094101· OSTI ID:1005850

Errandonea, D; Kumar, Ravhi S; Gracia, L; Beltrán, A; Achary, S N; Tyagi, A K

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 Laboratory (ANL)
• Sponsoring Organization: USDOE
• OSTI ID: 1005850
• Journal Information: Phys. Rev. B, Journal Name: Phys. Rev. B Journal Issue: (9) ; 2009 Vol. 80; ISSN 1098-0121
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

36 MATERIALS SCIENCE
COMPRESSIBILITY
CRYSTAL STRUCTURE
DENSITY FUNCTIONAL METHOD
EQUATIONS OF STATE
GERMANIUM OXIDES
PHASE TRANSFORMATIONS
PRESSURE RANGE GIGA PA
THORIUM OXIDES
X-RAY DIFFRACTION