Search results for "GST"
showing 10 items of 874 documents
High-pressure structural and lattice dynamical study ofHgWO4
2010
We have synthesized monoclinic mercury tungstate $({\text{HgWO}}_{4})$ and characterized its structural and vibrational properties at room conditions. Additionally, we report the structural and lattice dynamical behavior of ${\text{HgWO}}_{4}$ under high pressure studied by means of x-ray diffraction and Raman-scattering measurements up to 16 GPa and 25 GPa, respectively. The pressure dependence of the structural parameters and Raman-active first-order phonons of monoclinic $C2/c$ ${\text{HgWO}}_{4}$ are discussed in the light of our theoretical first-principles total-energy and lattice dynamics calculations. Our measurements show that the monoclinic phase of ${\text{HgWO}}_{4}$ is stable u…
A comparative study of heterostructured CuO/CuWO4 nanowires and thin films
2017
Authors are grateful to Reinis Ignatans for XRD measurements.
Post-spinel transformations and equation of state inZnGa2O4: Determination at high pressure byin situx-ray diffraction
2009
Room-temperature angle-dispersive x-ray diffraction measurements on spinel ZnGa{sub 2}O{sub 4} up to 56 GPa show evidence of two structural phase transformations. At 31.2 GPa, ZnGa{sub 2}O{sub 4} undergoes a transition from the cubic spinel structure to a tetragonal spinel structure similar to that of ZnMn{sub 2}O{sub 4}. At 55 GPa, a second transition to the orthorhombic marokite structure (CaMn{sub 2}O{sub 4}-type) takes place. The equation of state of cubic spinel ZnGa{sub 2}O{sub 4} is determined: V{sub 0} = 580.1(9) {angstrom}{sup 3}, B{sub 0} = 233(8) GPa, B'{sub 0} = 8.3(4), and B''{sub 0} = -0.1145 GPa{sup -1} (implied value); showing that ZnGa{sub 2}O{sub 4} is one of the less comp…
<title>Forward diffracted parametric X radiation from a thick Tungsten single crystal at 855 MeV electron energy</title>
2007
Features of forward diffracted Parametric X-Radiation (PXR) were investigated at experiments with the 855 MeV electron beam of the Mainz Microtron MAMI employing a 410 micrometer thick tungsten single crystal. Virtual photons from the electron field are diffracted by the (10-1) plane at a Bragg angle of 3.977 degree. Forward emitted radiation was analyzed at an energy of 40 keV with the (111) lattice planes of a flat silicon single crystal in Bragg geometry. Clear peak structures were observed in an angular scan of the tungsten single crystal. The results were analyzed with a model which describes forward diffracted PXR under real experimental conditions. The experiments show that forward d…
XAFS analysis of the low symmetry octahedral molybdenum and tungsten oxides
1995
Abstract Comparative XAFS analysis of the main isostructural crystalline phases of W(Mo)O3 oxides and W(Mo)O3·nH2O hydrates has been done at the W L3 and Mo K edges. These compounds have (1) 3D perovskite-type (PT) structure (m-WO3); (2) 2D PT structure (WO3·H2O and MoO3·nH2O (n = 1,2)); (3) 2D hexagonal-type structure (WO3·1/3H2O) and (4) 2D double layered structure (α-MoO3). The detailed analysis of X-ray absorption fine structure (XAFS) in the low-symmetry structures shows that in order to simulate the experimental spectrum, it is sufficient to take into account single-scattering contributions in the range from 1.7 to ∼ 5.0 A and a number of multiple-scattering paths from nearly linear a…
High-pressure structural phase transition inMnWO4
2015
The pressure-induced phase transition of the multiferroic manganese tungstate MnWO4 is studied on single crystals using synchrotron x-ray diffraction and Raman spectroscopy. We observe the monoclinic P2/c to triclinic P (1) over bar phase transition at 20.1 GPa and get insight on the phase transition mechanism from the appearance of tilted triclinic domains. Selective Raman spectroscopy experiments with single crystals have shown that the onset of the phase transition occurs 5 GPa below the previously reported pressure obtained from experiments performed with powder samples.
High-pressure theoretical and experimental study of HgWO4
2011
HgWO 4 at ambient pressure is characterized using a combination of ab initio calculations, X-ray diffraction and Raman scattering measurements. The effect of low pressure and temperature on the structural stability is analysed. Extending our ab initio study to the range of higher pressures, a sequence of stable phases up to 30GPa is proposed. © 2011 Taylor & Francis.
Polymorphism in Strontium Tungstate SrWO 4 under Quasi-Hydrostatic Compression
2016
The structural and vibrational properties of SrWO4 have been studied experimentally up to 27 and 46 GPa, respectively, by angle-dispersive synchrotron X-ray diffraction and Raman spectroscopy measurements as well as using ab initio calculations. The existence of four polymorphs upon quasi-hydrostatic compression is reported. The three phase transitions were found at 11.5, 19.0, and 39.5 GPa. The ambient-pressure SrWO4 tetragonal scheelite-type structure (S.G. I41/a) undergoes a transition to a monoclinic fergusonite-type structure (S.G. I2/a) at 11.5 GPa with a 1.5% volume decrease. Subsequently, at 19.0 GPa, another structural transformation takes place. Our calculations indicate two possi…
Politiķu priekšvēlēšanu kampaņas solījumu pildīšana: Donalda Trampa gadījums
2021
Darbs ir balstīts uz politiķu priekšvēlēšanas kampaņu programmām un tiek pētīts, kā politiķi pilda un pieturas savai priekšvēlēšanas kampaņas programmai, kas tiek izskatīts uz bijušā ASV Valsts prezidenta – Donalda Trampa piemēra. Darba mērķis ir izanalizēt Donalda Trampa 2015. gada priekšvēlēšanas kampaņas programmas saturu, atlasīt 5 galvenos programmas punktus un noskaidrot – vai tie tika izpildīti, vai nē, un tādā gadījumā, noskaidrot kādi bija iemesli neveiksmei. Teorētiskajā daļā tiek analizēta ASV federālā sistēma un tās ietekme uz ASV Valsts prezidenta rīcības iespējām, kā arī, priekšvēlēšanas kampaņas mērķis. Darbā tiek pielietota kvalitatīvā izpētes metode, kas paredz Donalda Tram…
Electrophysiological and behavioral studies in the evaluation of semiochemical attractants for Stegobium paniceum L. (Coleoptera: Anobiidae)
2017
Stegobium paniceum (L.) (Coleoptera: Anobiidae), also named drugstore beetle, is one of the major pests for a wide variety of dry and durable stored products. Females of this species produce a sex pheromone, (2S,3R,1’R)-Stegobinone that attracts males and elicit precopulatory searching behaviour. However, (2S,3R,1’R)-Stegobinone has eight possible isomers which are produced during its chemical synthesis and one of them inhibiting the pheromone activity, the (2S,3R,1'S)-Stegobinone form. In addition, the high costs of synthesis of (2S,3R,1’R)-Stegobinone suggest that alternative volatile compounds (e.g. those from food or oviposition sources) might be considered as attractant for traps. In t…