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991.
R. Chidambaram 《高压研究》2013,33(5-6):659-665
Abstract High pressure physics research at BARC spans a period of more than two decades and covers the area of both static and dynamic pressures on the one hand and both theoretical and experimental aspects on the other. The experimental facilities available include Diamond Anvil Cells for X-ray diffraction and Raman spectroscopy and a light gas gun. Phase transformations investigated in metallic systems includethose in Cd-Hg, transition metals, rare earths and actinides and these investigations have been supported by detailed band structure calculations and studies of the mechanismof phase transformations. Extensive equation of state studies over a wide range of pressures include a new model for the intermediate pressure range between 0.5 and 10 TPa and interpretation of experimental shock Hugoniots. 相似文献
992.
Abstract Energy Dispersive X-ray Diffraction (EDXD) was performed at room temperature to gather structural data on CaS between approximately 1.7 GPa to nearly 150GPa. In these experiments, CaS retained the B1 structure up to approximately 40 GPa above which it began to transform to the B2 structure. The B2 structure remained stable to the highest pressure reached, 149 GPa, where the relative volume V/V0 was 0.490. Previous studies on CaS extended only up to 52 GPa, which is barely 10 GPa after the B1 phase changes to the B2 structure. Thus it was not possible to accurately extrapolate the equation of state (EOS) for the B2 phase region to significantly higher pressures. In the present study EOS data for CaS was collected to 150 GPa and no other structural change was observed. EOS parameters for the B1 and B2 phase regions agree well with values reported in the literature. 相似文献
993.
J. Arvanitidis K. P. Meletov G. A. Kourouklis K. Papagelis A. Soldatov K. Prassides 《高压研究》2013,33(1-6):145-151
Abstract The effect of high hydrostatic pressure, up to 12GPa, on the intramolecular phonon frequencies and the material stability of the two-dimensional tetragonal Cm polymer has been studied by means of Raman spectroscopy in the spectral range of the radial intramolecular modes (200-800cm?1). A number of new Raman modes appear in the spectrum for pressures ~ 1.4 and ~ 5.0 GPa. The pressure coefficients for the majority of the phonon modes exhibit changes to lower values at P=4.0 GPa, which may be related to a structural modification of the 2D polymer to a more isotropic phase. The peculiarities observed in the Raman spectra are reversible and the material is stable in the pressure region investigated. 相似文献
994.
M. Giffhorn B. Becker A. A. Menovsky J. A. Mydosh G. J. Nieuwenhuys S. Ramakrishnan 《高压研究》2013,33(1-6):159-163
Abstract An uniaxial pressure cell for low temperature use is described in detail. Then we present data of the electrical resistance of single crystals of Lu5Ir4Si10, which is known to show a charge-density-wave transition around 83 K and to become superconducting near 3.8 K, both phenomena being anticorrelated under pressure. Since the CDW in Lu5Ir4Si10 is a quasi one-dimensional phenomenon because of a chain-like structure, it responds to uniaxial pressure in a specific way. 相似文献
995.
Hideki Yoshizawa Yasuaki Oohara Yasushi Okayama Hiroki Takahashi Nobuo Môri Setsuo Mitsuda 《高压研究》2013,33(4-6):413-418
Abstract We have determined the magnetic structure of a low-carrier Kondo-lattice system CeAs, and have observed a softening of the crystalline electric field excitations. Despite the prediction of a recent magnetic polaron model in which CeAs and CeP are expected to show a stacking order of T7 and T8 layers, CeAs does not show such a stacking structure under pressure. The ordering in the intermediate phase is a regular ferromagnetic order and that of the low-temperature phase is a canted type-I AF. 相似文献
996.
Abstract Energy-dispersive x-ray diffraction using synchrotron radiation was carried out on α-cristobalite to 3 GPa and 350°C in a cubic anvil press. A cascading structural phase transition occurred beyond 0.61 GPa at room temperature. The transition was accompanied by a splitting of most of the a-cristobalite reflections: the (111) reflection at 0.61 GPa through the (211) reflections at 2.13 GPa, with many other lines between. The pressure of this transition decreased with increasing temperature. 相似文献
997.
Abstract The displacive transition in La is studied in the pressure range up to 26 GPa and under temperatures up to 630 K with angular dispersive X-ray diffraction at the ESRF and with energy dispersive X-ray diffraction in HASYLAB to elucidate further details of this transition with an extension of the transition line up to 22.5(5) GPa and 590(10) K and a determination of the order parameter down to a level of η ≈=5· 10?4. 相似文献
998.
Abstract Neptunium and plutonium monosulfides were studied under high pressure up to ~60 GPa using a diamond anvil cell in an energy dispersive X-ray diffraction facility. The compounds, of cubic rock salt structure type at ambient pressure, do not show any crystallographic phase transition in the domain of investigation. From the pressure-volume relationship, we determined bulk moduli of 92 and 120 GPa with pressure derivatives of 4.6 and 4.1 for NpS and PUS respectively. 相似文献
999.
Abstract Two piston/cylinder type pressure cells for neutron powder diffraction are presented. They provide a large sample volume and hence allow rapid data collection at moderate flux neutron sources. Structure refinements from the diffraction data are possible. The maximum attainable pressure is above 2 GPa for Ti/Zr zero-scattering pressure cylinders. Both cells may be equipped with a micro-furnace. This allows measurement up to 700 K, simultaneously to the application of pressure. The low temperature setup for the cell-I is presented which will allow experiments down to 1·5K. 相似文献
1000.
Abstract The knowledge of water exchange reaction mechanism in aqueous solutions of Gd3+ polyaminocarboxylates is important for the understanding of the relatively slow water exchange rates measured for these complexes. Variable ressure measurements show a change of mechanism from associatively activated on [Gd(H2O)8]3+ and [Gd(PDTA)(H2O2)2]? to probably limiting dissociative on the MRI contrast agents [Gd(DOTA)(H2O)]?, [Gd(DTPA)(H2O)]2? and [Gd(DTPA-BMA)(H2O)]. 相似文献