0000000001311046
AUTHOR
Avesh K. Tyagi
ChemInform Abstract: New Polymorph of InVO4: A High-Pressure Structure with Six-Coordinated Vanadium.
High-pressure XRD and Raman spectroscopy on orthorhombic InVO4 (space group Cmcm, Z = 4) reveal the existence of a new wolframite-type polymorph of InVO4 near 7 GPa.
ChemInform Abstract: Pressure-Induced Transformations in PrVO4and SmVO4and Isolation of High-Pressure Metastable Phases.
High-pressure phases of PrVO4 and SmVO4 are synthesized from the zircon-structured compounds at 12 GPa and room temperature (24 h).
High-pressure structural and vibrational properties of monazite-type BiPO4, LaPO4, CePO4, and PrPO4
[EN] Monazite-type BiPO4, LaPO4, CePO4, and PrPO4 have been studied under high pressure by ab initio simulations and Raman spectroscopy measurements in the pressure range of stability of the monazite structure. A good agreement between experimental and theoretical Raman-active mode frequencies and pressure coefficients has been found which has allowed us to discuss the nature of the Raman-active modes. Besides, calculations have provided us with information on how the crystal structure is modified by pressure. This information has allowed us to determine the equation of state and the isothermal compressibility tensor of the four studied compounds. In addition, the information obtained on th…
High-pressure x-ray diffraction study of CdMoO4 and EuMoO4
International audience; We studied the effects of high pressure on the crystalline structure of scheelite-type CdMoO4 and EuMoO4. We found that the compressibility of the materials is highly nonisotropic, with the c-axis being the most compressible one. We also observed clear evidence of a structural phase transition at 12 GPa (CdMoO4) and 8.8 GPa (EuMoO4). The high-pressure phase has a monoclinic structure similar to M-fergusonite. The transition is reversible, and no volume change is detected between the low- and high-pressure phases. The results contradict early x-ray diffraction studies carried out in CdMoO4 and are compared with those obtained previously in isomorphic molybdates. Final…
Pressure Impact on the Stability and Distortion of the Crystal Structure of CeScO3
[EN] The effects of high pressure on the crystal structure of orthorhombic (Pnma) perovskite-type cerium scandate were studied in situ under high pressure by means of synchrotron X-ray powder diffraction, using a diamond-anvil cell. We found that the perovskite-type crystal structure remains stable up to 40 GPa, the highest pressure reached in the experiments. The evolution of unit-cell parameters with pressure indicated an anisotropic compression. The room-temperature pressure¿volume equation of state (EOS) obtained from the experiments indicated the EOS parameters V0 = 262.5(3) Å3 , B0 = 165(7) GPa, and B0¿ = 6.3(5). From the evolution of microscopic structural parameters like bond distan…
High-pressure polymorphs of TbVO4: A Raman and ab initio study
Raman measurements on TbVO4 show the occurrence of three pressure-induced phase transitions. The first one, an irreversible transition from the zircon to the scheelite structure, occurs beyond 6.7 GPa. In addition, two reversible transformations take place at 26.7 and 34.4 GPa. The last transition was never reported before. The experimental findings are supported by structural and lattice-dynamics calculations that helped us to identify the post-scheelite phase as a monoclinic fergusonite structure. According to the calculations, the third transition involves a symmetry increase. An orthorhombic structure is proposed for the phase found above 34.4 GPa. The results have been compared with pr…
New polymorph of InVO4: A high-pressure structure with six-coordinated vanadium
A new wolframite-type polymorph of InVO4 is identified under compression near 7 GPa by in situ high-pressure (HP) X-ray diffraction (XRD) and Raman spectroscopic investigations on the stable orthorhombic InVO4. The structural transition is accompanied by a large volume collapse (Delta V/V = -14%) and a drastic increase in bulk modulus (from 69 to 168 GPa). Both techniques also show the existence of a third phase coexisting with the low- and high-pressure phases in a limited pressure range close to the transition pressure. XRD studies revealed a highly anisotropic compression in orthorhombic InVO4. In addition, the compressibility becomes nonlinear in the HP polymorph. The volume collapse in…
High-pressure structural investigation of several zircon-type orthovanadates
Room temperature angle-dispersive x-ray diffraction measurements on zircon-type EuVO4, LuVO4, and ScVO4 were performed up to 27 GPa. In the three compounds we found evidence of a pressure-induced structural phase transformation from zircon to a scheelite-type structure. The onset of the transition is near 8 GPa, but the transition is sluggish and the low- and high-pressure phases coexist in a pressure range of about 10 GPa. In EuVO4 and LuVO4 a second transition to a M-fergusonite-type phase was found near 21 GPa. The equations of state for the zircon and scheelite phases are also determined. Among the three studied compounds, we found that ScVO4 is less compressible than EuVO4 and LuVO4, b…
Experimental and Theoretical Investigations on Structural and Vibrational Properties of Melilite-Type Sr2ZnGe2O7 at High Pressure and Delineation of a High-Pressure Monoclinic Phase.
We report a combined experimental and theoretical study of melilite-type germanate, Sr2ZnGe2O7, under compression. In situ high-pressure X-ray diffraction and Raman scattering measurements up to 22 GPa were complemented with first-principles theoretical calculations of structural and lattice dynamics properties. Our experiments show that the tetragonal structure of Sr2ZnGe2O7 at ambient conditions transforms reversibly to a monoclinic phase above 12.2 Gpa with similar to 1% volume drop at the phase transition pressure. Density functional calculations indicate the transition pressure at, similar to 13 GPa, which agrees well with the experimental value. The structure of the high-pressure mono…
ChemInform Abstract: Experimental and Theoretical Investigations on Structural and Vibrational Properties of Melilite-Type Sr2ZnGe2O7at High Pressure and Delineation of a High-Pressure Monoclinic Phase.
The title compound is characterized by high-pressure powder XRD and Raman scattering measurements up to 22 GPa, and by DFT calculations.
Pressure-Induced Transformations in PrVO4 and SmVO4 and Isolation of High-Pressure Metastable Phases
Zircon-type PrVO4 and SmVO4 have been studied by high-pressure Raman spectroscopy up to 17 GPa. The occurrence of phase transitions has been detected when compression exceeds 6 GPa. The transformations are not reversible. Raman spectra of the high-pressure phases show similarities with those expected for a monazite-type phase in PrVO4 and a scheelite-type phase in SmVO4.The high-pressure phases have been also synthesized using a large-volume press and recovered at ambient conditions. X-ray diffraction measurements of the metastable products recovered after decompression confirms the monazite (PrVO4) and scheelite (SmVO4) structures of the high-pressure phases. Based upon optical properties …
Pressure-Induced Hexagonal to Monoclinic Phase Transition of Partially Hydrated CePO4
We present a study of the pressure dependence of the structure of partially hydrated hexagonal CePO 4 up to 21 GPa using synchrotron powder X-ray diffraction. At a pressure of 10 GPa, a second-order structural phase transition is observed, associated with a novel polymorph. The previously unknown high-pressure phase has a monoclinic structure with a similar atomic arrangement as the low-pressure phase, but with reduced symmetry, belonging to space group C2. Group-subgroup relations hold for the space symmetry groups of both structures. There is no detectable volume discontinuity at the phase transition. Here we provide structural information on the new phase and determine the axial compress…
Zircon to monazite phase transition in CeVO4: X-ray diffraction and Raman-scattering measurements
X-ray diffraction and Raman-scattering measurements on cerium vanadate have been performed up to 12 and 16 GPa, respectively. Experiments reveal at 5.3 GPa the onset of a pressure-induced irreversible phase transition from the zircon to the monazite structure. Beyond this pressure, diffraction peaks and Raman-active modes of the monazite phase are measured. The zircon-to-monazite transition in CeVO4 is distinctive among the other rare-earth orthovanadates. We also observed softening of external translational T(Eg )a nd internalν2(B2g) bending modes. We attribute it to mechanical instabilities of zircon phase against the pressure-induced distortion. We additionally report lattice-dynamical a…
Stability of FeVO4 under Pressure: An X-ray Diffraction and First-Principles Study
The high-pressure behavior of the crystalline structure FeVO4 has been studied by means of X-ray diffraction using a diamond-anvil cell and first-principles calculations. The experiments were carried out up to a pressure of 12.3 GPa, until now the highest pressure reached to study an FeVO4 compound. High-pressure X-ray diffraction measurements show that the triclinic P1 (FeVO4-I) phase remains stable up to ≈3 GPa; then a first-order phase transition to a new monoclinic polymorph of FeVO4 (FeVO4-II′) with space group C2/m is observed, having an α-MnMoO4-type structure. A second first-order phase transition is observed around 5 GPa toward the monoclinic (P2/c) wolframite-type FeVO4-IV structu…
High-pressure crystal structure, lattice vibrations, and band structure of BiSbO4
The high-pressure crystal structure, lattice-vibrations HP crystal structure, lattice vibrations, and band , and electronic band structure of BiSbO4 were studied by ab initio simulations. We also performed Raman spectroscopy, infrared spectroscopy, and diffuse-reflectance measurements, as well as synchrotron powder X-ray diffraction. High-pressure X-ray diffraction measurements show that the crystal structure of BiSbO4 remains stable up to at least 70 GPa, unlike other known MTO4-type ternary oxides. These experiments also give information on the pressure dependence of the unit-cell parameters. Calculations properly describe the crystal structure of BiSbO4 and the changes induced by pressur…
CSD 976492: Experimental Crystal Structure Determination
Related Article: Daniel Errandonea, Oscar Gomis, Braulio García-Domene, Julio Pellicer-Porres, Vasundhara Katari, S. Nagabhusan Achary, Avesh K. Tyagi, and Catalin Popescu|2013|Inorg.Chem.|52|12790|doi:10.1021/ic402043x
CSD 1879403: Experimental Crystal Structure Determination
Related Article: Enrico Bandiello, Daniel Errandonea, Sergio Ferrari, Julio Pellicer-Porres, Domingo Mart��nez-Garc��a, S. Nagabhusan Achary, Avesh K. Tyagi, Catalin Popescu|2019|Inorg.Chem.|58|4480|doi:10.1021/acs.inorgchem.8b03648
CSD 1879404: Experimental Crystal Structure Determination
Related Article: Enrico Bandiello, Daniel Errandonea, Sergio Ferrari, Julio Pellicer-Porres, Domingo Mart��nez-Garc��a, S. Nagabhusan Achary, Avesh K. Tyagi, Catalin Popescu|2019|Inorg.Chem.|58|4480|doi:10.1021/acs.inorgchem.8b03648
CSD 976491: Experimental Crystal Structure Determination
Related Article: Daniel Errandonea, Oscar Gomis, Braulio García-Domene, Julio Pellicer-Porres, Vasundhara Katari, S. Nagabhusan Achary, Avesh K. Tyagi, and Catalin Popescu|2013|Inorg.Chem.|52|12790|doi:10.1021/ic402043x