Showing papers in "High Pressure Research in 1998"
TL;DR: The historical and theoretical background for the different mathematical forms commonly used to represent equations of state (EOS) for solids is reviewed and some criteria are discussed which allow to select some specific forms, which are not only convenient mathematical forms but bring out the physical meaning of the data as mentioned in this paper.
Abstract: The historical and theoretical background for the different mathematical forms commonly used to represent equations of state (EOS) for solids is reviewed and some criteria are discussed which allow to select some specific forms, which are not only convenient mathematical forms but bring out the physical meaning of the data. Some examples are discussed with emphasis on recent experimental and theoretical data including noble gas solids, simple metals and a few metals with special “anomalies” to illustrate the differences involved in the use of different EOS forms and to point out the specific physical reasons for differences in specific EOS forms.
76 citations
TL;DR: In this paper, a series of plate impact experiments have provided evidence for the appearance of failure waves in glasses under uniaxial compression, and it was found that failure wave can be initiated on both the impact surface and the internal surface inside the sample, indicating that the glass surface is a direct source for the failure wave nucleation.
Abstract: Previously, a series of plate impact experiments have provided evidence for the appearance of failure waves in glasses under uniaxial compression. Presented herein is a continuation of research, performed on K9 crown glass and ZF1 dense flint glass at varied shock stresses with a goal to uncover the failure wave source and to make clear whether or not the failure wave can be formed at stresses above the Hugoniot elastic limit (HEL). It has been found that, at peak stresses below the HEL, the failure wave can be initiated on both the impact surface and the internal surface inside the sample, indicating that the glass surface is a direct source for the failure wave nucleation. However, when the peak stress exceeds the HEL, brittle glasses become ductile as a result of irreversible densification, and the Failure wave disappears. The high spall strength revealed in the stress range above the HEL indicates that ductility is also preserved under the subsequent tension.
21 citations
TL;DR: In this paper, the effect of pressure on acceptor levels and hole scattering mechanisms in p-GaSe was investigated through Hall effect and resistivity measurements under quasi-hydrostatic conditions up to 4 GPa.
Abstract: The effect of pressure on acceptor levels and hole scattering mechanisms in p-GaSe is investigated through Hall effect and resistivity measurements under quasi-hydrostatic conditions up to 4 GPa. The pressure dependence of the hole concentration is interpreted through a carrier statistics equation with a single (nitrogen) or double (tin) acceptor whose ionization energies decrease under pressure due to the dielectric constant increase. The pressure effect on the hole mobility is also accounted for by considering the pressure dependencies of both the phonon frequencies and the hole-phonon coupling constant involved in the scattering rates.
12 citations
TL;DR: In this paper, the crystal structure of the solid I phase of bromobenzene at room temperature was determined at pressure around 0.4 GPa, and the solid II phase transformed into an amorphous phase.
Abstract: Raman scattering and powder x-ray diffraction experiments have been carried out on solid bromobenzene up to 20 GPa at room temperature in diamond anvil cells. At room temperature, bromobenzene solidifys at pressure around 0.4 GPa and the crystal structure of the solid I phase is proposed to be Pbcn with eight molecules per unit cell, which is the same as that of chlorobenzene. The structural phase transition from the orthorhombic solid I phase to the solid II phase takes place at pressure around 4 GPa, its crystal structure, however, is not determined yet. With further increase in pressure, the solid II phase transformed into an amorphous phase.
4 citations
TL;DR: In this paper, the phase compositions of (La1-xSnx)(2)(Mn0.985Fe0.015)(2)O-y are strongly dependent on the Sn concentrations and on the heat treatment.
Abstract: Mossbauer spectra of (La1-xSnx)(2)(Mn0.985Fe0.015)(2)O-y (x = 0.2, 0.3, 0.4 and 0.5) from room temperature to 4.2 K have been studied; in addition X-ray diffraction patterns at room temperature have been obtained. The results show that the phase compositions of (La1-xSnx)(2)(Mn0.985Fe0.015)(2)O-y are strongly dependent on the Sn concentrations and on the heat treatment. The manganites with a: = 0.2, 0.3 and 0.4 after annealing in air at 1200 degrees C appear to consist of two phases, ABO(3) and A(2)B(2)O(7) Their Mossbauer spectra are paramagnetic doublets at room temperature that become sextets at T similar to 230 K and similar to 60 K. The ABO(3) phase appears to be the source of the CMR in manganite (La0.7Sn0.3)(2)(Mn0.985Fe0.015)(2)O-y.
3 citations
TL;DR: In this article, the authors studied the compression behavior of Ni3A1 in a pressure medium of NaCl and showed that the divergence in lattice spacings calculated from multiple orders of reflections can be explained from the introduction of stacking faults.
Abstract: The compression behavior of a foil of Ni3A1 in a pressure medium of NaCl has been studied by energy-dispersive X-ray diffraction in a diamond anvil cell. Increasingly non-hydrostatic conditions lead to a region of incompressibility starting at around 3 GPa and terminated by a discontinuity in the compressibility at 7 GPa. Strong line broadening indicating plastic deformation starts at 3 GPa and continues to above 7 GPa. Direct compression of a foil between the diamonds results in a strong divergence in lattice parameters calculated from different lattice spacings and a volume incompressibility terminated by a discontinuity in the compressibility. The divergence in lattice spacings calculated from multiple orders of reflections can be explained from the introduction of stacking faults. The trend with pressure of the divergence agrees with that of the line profiles suggesting that these are to a large extent due to stacking faults. Comparison with earlier results for Cu3Au in identical experiments ...
3 citations
TL;DR: In this article, solid state reaction of Mg with Ni was processed under static high pressure and nanocrystalline Mg2Ni was obtained, and an unknown phase was also formed at lower temperature.
Abstract: Solid state reaction of Mg with Ni was processed under static high pressure and nanocrystalline Mg2Ni was obtained. An unknown phase was also formed at lower temperature. The relation between the mean grain size of Mg2Ni and the synthetizing pressure is given, and its mechanism is discussed.
2 citations
TL;DR: In this paper, a liquid zinc sample has been solidified by rapid pressurization, and in situ differential thermal analysis was performed during the solidification process, and the TEM results showed that nanocrystalline zinc sample was obtained.
Abstract: Liquid zinc sample have been solidified by rapid pressurization. In situ differential thermal analysis was performed during the solidification process, and the TEM results show that nanocrystalline zinc sample was obtained. The rapid pressurization solidification reported here is a new way to form nanocrystallites in bulk materials.
1 citations
TL;DR: In this article, the binding energies as a function of pressure up to 4 Gpa for on-centre shallow donor impurities in a spherical GaAs-Ga1-x, Alx, As quantum dot for both finite and infinite barriers following a variational procedure within the effective mass approximation including the spatial variation of dielectric screening.
Abstract: We have calculated the binding energies as a function of pressure up to 4 Gpa for on-centre shallow donor impurities in a spherical GaAs-Ga1-x, Alx, As quantum dot for both finite and infinite barriers following a variational procedure within the effective mass approximation including the spatial variation of dielectric screening. Results reveal that the characteristics of variation of donor binding energy with dot radius at a given pressure is the same as those at zero pressure, and the binding energies increase with the increase of pressure. The increase becomes more and more as the dot radius decreases. The effect of pressure are similar to the effects due to the variation of A1 concentration x.