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1.
Abstract Synthetic Type 1b yellow diamonds containing nitrogen in substitutional form and with extremely low birefringence were used as anvils for ultra high pressures in the diamond anvil cell. Pressures were measured by the ruby fluorescence technique to above 200 GPa. Using x-ray diffraction the maximum pressure was 210 GPa, while an x-ray based pressure of 245 GPa was achieved with natural diamonds with a somewhat more optimal geometry. Nitrogen platelets appear to be not essential for exceeding 200 GPa. The optical properties of synthetic diamond at ambient and megabar stresses will be discussed. 相似文献
2.
We have investigated the pressure effects on the structural properties of C 6 O 2 I 4 up to 39 GPa by powder x-ray diffraction measurements, which were compared with those of C 6 I 6 . The diffraction patterns of C 6 O 2 I 4 indicated a phase transition starting at 26.8 GPa. The mixed state of the low- and high-pressure phases continued up to 39 GPa well above an insulator-to-metal transition pressure of 33 GPa. The C 6 O 2 I 4 molecule remains planar structure in the low-pressure phase below 26.8 GPa in contrast to the non-planar molecular structure of C 6 I 6 at ambient and high pressures. 相似文献
3.
Ulrich Benedict Claude Dufour Stephen Heathman Tristan Le Bihan Janus Staun Olsen Leif Gerward 《高压研究》2013,33(4-6):393-404
Abstract Uranium and thorium have sufficiently low radioactive dose rates to allow their study at synchrotrons and neutron facilities. Correspondingly, numerous compounds of these two actinides have been studied under pressure by synchrotron x-ray diffraction. The maximum pressures reached were on the order of 60-80 GPa, and 300 GPa in one case. The situation is much more difficult for all other actinides. Their high level of radioactivity has up to now prevented their study at synchrotrons, except in a few special cases. In contrast, all actinide metals available in sufficient quantities, and a large number of compounds of highly radioactive actinides, have been studied in highpressure laboratory facilities. Recent examples of in situ high pressure x-ray diffraction work will be described. 相似文献
4.
Donald J. Weidner Michael T. Vaughan Jaidong Ko Yanbin Wang Kurt Leinenweber Xing Liu Amir Yeganeh-Haeri 《高压研究》2013,33(5-6):617-623
Abstract A DIA-type cubic-anvil high pressure apparatus (SAM-85) has been interfaced with white x-ray radiation from the superconducting wiggler port of the National Synchrotron Light Source at Brookhaven National Laboratory. Energy-dispersive x-ray diffraction measurements can be obtained for samples with dimensions of the order of 1 mm as a function of pressure and temperature utilizing x-ray energies of up to100 keV. The sample environment is examined. Pressure is uniform in the sample chamber to within 0.1 GPa, and temperature is constant in the scattering volume to within 5°C.A method is defined for determining deviatoric stress. We find that for a sample containing NaCl and Au, the deviatoric stress increases to about 0.3 GPa as pressure increases to 1.5 GPa and then remains constant, probably reflecting the strength of the sample. Upon heating, the deviatoric stress quickly approaches zero. Presented at the IUCr Workshop on ‘Synchrotron Radiation Instrumentation for High Pressure Crystallography’, Daresbury Laboratory 20-21 July 1991 相似文献
5.
Abstract We have developed two Merrill-Bassett diamond-anvil cells for specialized high-temperature uses. The first is constructed largely of rhenium to provide uniform, constant P and T on the order of 20 GPa at 1200 K for extended periods. The second is for single-crystal x-ray diffraction, but can be heated to 630 K at 20 GPa to grow single-crystal samples which cannot be produced at room temperature. With this cell, the crystal structure of ?-O2 was shown to be monoclinic with a = 3.649 A, b = 5.493 A, c = 7.701 A, and β = 116.11° at 19.7 GPa. 相似文献
6.
Abstract Review of phase transitions and equations of state at multimegabar pressures (100–300 GPa) is presented. Energy dispersive x-ray diffraction techniques in conjunction with synchrotron radiation sources are used. Besides several transition metals, Pt to 282 GPa, Re to 251 GPa, W to 209 GPa, and Fe to 255 GPa, the special focus is on Group IVA elements and isoelectronic III-V compounds. At high pressure, the isoelectronic materials are isostructural and exhibit similar equation of state. 相似文献
7.
Abstract α-Quartz was compressed at room temperature in a diamond-anvil cell without a medium to maximum pressures of 31 to 213 GPa and was studied by energy-dispersive synchrotron X-ray diffraction. Broad peaks observed in a previous high-pressure diffraction study of silica glass are evident in the present study of quartz compression, providing in situ confirmation of pressure-induced amorphization above 21 GPa. The 21-GPa crystalline-crystalline (quartz 1–11) transformation previously observed on quasihydrostatic compression of quartz is found to also occur under the current nonhydrostatic conditions, at the identical pressure. With nonhydrostatic compression, however, new sharp diffraction lines are observed at this pressure. The measurements show the coexistence of at least one amorphous and two crystalline phases above 21 GPa and below 43 GPa. The two crystalline phases are identified as quartz II and a new, high-pressure silica phase. The high-pressure phases, both crystalline and amorphous, can be quenched to ambient conditions from a maximum pressure of 43 GPa. With compression above 43 GPa, the diffraction pattern from quartz II is lost and the second crystalline phase persists to above 200 GPa. 相似文献
8.
Abstract The structural energy differences have been calculated for zirconium as a function of pressure at zero temperature using the Andersen force theorem and the linear muffin tin orbital method. The structures included are the following: α (hcp), the room temperature room pressure phase, ω- a three atom simple hexagonal, bcc and fcc. Our calculations show that the bcc structure would become energetically most favourable above 11 GPa. This results is in agreement with well known correlation between the crystal structure and the d-electron population in transition metals at normal volume. The diamond anvil cell based high pressure x-ray diffraction experiments are in progress to verify this result. 相似文献
9.
Abstract The trivalent rare-earth element gadolinium has been studied up to 8 GPa and 700°C by energy-dispersive synchrotron x-ray diffraction. Except for the known crystal structures of hcp, Sm-type, and dhcp, no long-period polytypes have been observed. It is found that the hcp structure transforms directly to the dhcp structure with increasing pressure at high temperatures. 相似文献
10.
Abstract The transition to the β tin structure has been observed by X-ray absorption spectroscopy for GaSb at 7.9 GPa. In the low pressure phase, the bulk modulus has been determined. In the high pressure phase, the results for the Ga-Sb and Ga-Ga distances are in good agreement with previous x-ray diffraction data. The pseudo Debye-Waller factor associated to the Ga-Sb distance is abnormally high, indicating that disorder exists for this bond. 相似文献
11.
H. Olijnyk 《高压研究》2013,33(1-6):313-315
Abstract High pressure x-ray diffraction studies at room temperature indicate the δ → ? phase transition at 16. 3 GPa. The room temperature isotherm is determined and compared with the results of a Priori calculations. 相似文献
12.
Arthur L. Ruoff 《高压研究》2013,33(5-6):639-645
Abstract We have now taken two materials (W, Mo) to pressures greater than the pressure at the center of the earth for the first time, with all pressures based on x-ray diffraction and shock-based equations of state. The present paper describes x-ray diffraction studies of a sample in which pressure equals or exceeds 438 GPa. It is noted that as a result of the process of pressure strengthening, pressures of 1 TPa may be attainable. Presented at the IUCr Workshop on ‘Synchrotron Radiation Instrumenration for HighPressure Crystallography’. Daresbury Laboratory 20-21 July 1991 相似文献
13.
Abstract PbSe/SnSe superlattice, phase transition, high pressure, SR x-ray diffraction) Synchrotron x-ray diffraction experiments have revealed successive phase transitions in epitaxially-grown PbSe/SnSe superlattices. The transition pressures from the low-pressre cubic B1- to the high-pressure orthorhombic B16-type structures are observed to vary systematically depending upon thickness of the PbSe layer. For example, a [PbSe(36A)/SnSe(12A)]19, with the B1 structure in both layers stabilized in its asgrown state, undergoes the [B1/B1]-to-[B1/B16] and [B1/B16]-to-[B16/B16] structural transitions at 1.9 and 3.8GPa, respectively. This result is in contrast to their bulk data that the B1-to-B16 transition takes place at 5.3GPa in PbSe while the B16 phase is stable in SnSe at atmospheric pressure. 相似文献
14.
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
15.
Abstract Lattice parameters of SrFCl have been measured by powder x-ray diffraction up to 38 GPa. Furthermore, energy levels and crystal field parameters of Sm2+ in SrFCl have been determined from fluorescence spectra at 100 K under pressures up to 10 GPa. 相似文献
16.
Abstract We have investigated the high pressure behavior of InSe by x-ray powder diffraction and optical measurements. The rhombohedral γ-polytype of InSe (space group R3m) exhibits a strongly anisotropic compressibility characteristic of the layer-type structure. Mode Gruneisen parameters of intralayer modes have been determined by Raman scattering. At 10.3(5) GPa InSe undergoes a phase transition to the rocksalt structure, which remains stable up to at least 30 GPa. Optical reflectivity measurements show the cubic high pressure phase to have metallic character. 相似文献
17.
Abstract X-ray diffraction measurements have been carried out above 300 GPa for the first time using Pt as a primary pressure standard. The equations of state of iron up to 304 GPa and of CsI up to 302 GPa have been obtained. These materials can therefore be used as secondary pressure calibrants. 相似文献
18.
V. A. Davydov L. S. Kashevarova A. V. Rakhmanina V. M. Senyavin V. Agafonov R. Ceolin H. Szwarc 《JETP Letters》1998,68(12):928-934
The dimerization of C60 fullerene under conditions of quasi-hydrostatic compression at temperatures above 293 K is investigated by IR spectroscopy,
Raman scattering (RS) spectroscopy, and x-ray diffraction. The measured dimer (C60)2 content in the products of the polymerization of fullerite as a function of the pressure, temperature, and treatment time
shows that dimerization occurs even at room temperature in the entire pressure range above ∼1.0 GPa. However, at least at
temperatures above 400 K dimerization does not result in the formation of a dimer phase as a stable modification of the system,
since the dimer is an intermediate product of the transformation. It is shown that increasing the holding time at 423 K decreases
the content of the dimer fraction in the samples and results in the formation of linear (at 1.5 GPa) and two-dimensional (at
6.0 GPa) polymers, which are structure-forming elements of the orthorhombic and rhombohedral polymerized phases.
Pis'ma Zh. éksp. Teor. Fiz. 68, No. 12, 881–886 (25 December 1998) 相似文献
19.
Abstract Powder x-ray diffraction experiments have been performed on 2H-CsCdBr3. at room temperature up to 25 GPa. At normal pressure this compound shows unidimensional electronic properties. Such unidimensional behaviour is not evident in terms of elastic bulk properties under pressure. No phase transformation occurs in this pressure range. The a and c lattice parameters steadily decrease with pressure; their ratio lowers by only 2% up to 25 GPa. The bulk modulus is low, 21.2 GPa, and is in very good agreement with the bulk modulus-volume systematics for ionic compounds. The value of the first pressure derivative is also typical of ionic compounds. 相似文献
20.
Abstract The crystal structure of ThS2, ThSe2 and US2 has been investigated for pressure up to 60GPa using x-ray powder diffraction. The bulk moduli are 175(10), 155(10) and 155(20) GPa, respectively. A pressure-induced phase transformation occurs at about 40 GPa for ThS2, 30 GPa for ThSe2 and 15 GPa for US2. The results for ThSe2 indicate that its high-pressure phase has a monoclinic structure. The same structure is compatible with the observed high-pressure spectra of ThS2 and US2. However, the crystal system assignment is less certain for these compounds. 相似文献