Pressure In Diamond Anvil Cell Research Articles

High-pressure optical study of f–d hybridization in U xLa 1−xS single crystals

The optical reflectivity of U x La 1− x S single crystals has been measured in a diamond-anvil cell for pressures up to 40 GPa. From a fit of the reflectivity spectra with one Drude term and three Lorentz oscillators the energies, intensities and widths of optical transitions are derived. In contrast to the expectation in an itinerant picture, the plasma frequencies decrease with increasing pressure, indicating the dominance of f–d hybridization effects. The non-monotonic variation with x of the plasma frequencies and the oscillator strengths of interband transitions supports the model of the simultaneous presence of localized and itinerant 5f states in U x La 1− x S.

Absorption corrections for diamond-anvil pressure cells implemented in the software packageAbsorb6.0

High-pressure single-crystal structure refinement requires intensity data that have been corrected for the various absorption effects in the pressure cell. In this contribution, the methods for calculating the absorption corrections for a transmission-geometry diamond-anvil pressure cell are reviewed. The ideas presented in this paper have been implemented in a software package for Microsoft Windows,Absorb6.0, available at http://www.crystal.vt.edu/.

Equation of state and structural changes in diaminodinitroethylene under compression.

Structural changes in 1,1-diamino-2,2-dinitroethylene (DADNE, FOX-7) compressed to high pressure in diamond anvil cells were investigated using angle-dispersive x-ray diffraction analysis, Raman spectroscopy, and optical polarizing microscopy. The x-ray results show several changes above 1 GPa. When the x-ray data are indexed according to the ambient-pressure structure, DADNE shows anisotropic compression, with higher compression along the b axis than along the a or c axis. An ambient-temperature isothermal equation of state of DADNE was generated from these data. In addition, the experimentally obtained Raman spectra were matched with vibrational normal modes calculated using quantum chemistry calculations. The shifts in vibrational modes indicate changes in H-wagging vibrations with pressure.

Electrical resistance measurement on a ferromagnetic element Gadolinium under high pressure

We performed the electrical resistance measurement on a ferromagnetic rare earth element gadolinium (Gd) under high pressure using a diamond anvil pressure cell. The ferromagnetic transition temperature seems to be almost constant against the pressure and slightly increase above 3 GPa . The present experimental results are discussed in comparison with previous studies by the X-ray and the magnetization measurements on this element.

Brillouin scattering at high pressure: an overview

AbstractBrillouin scattering allows the determination of acoustic velocities and adiabatic elastic moduli in matter. These data are crucial in many areas of science, such as fundamental physics, geosciences and technology, especially when measured as a function of the density (pressure). In this paper, we present a review of the work performed on Brillouin scattering under high pressure in diamond anvil cells, emphasizing the most recent results. Copyright © 2003 John Wiley & Sons, Ltd.

Effect of pressure on zone-center phonons in hexagonal-close-packed metals

We report on studies of several hexagonal-close-packed (hcp) metals by Raman scattering techniques in the diamond anvil cell for pressures up to 60 GPa. The pressure response of the observed transverse-optical (TO) zone-center phonon mode includes positive pressure shifts as well as anomalies, such as mode softening in connection with phase transitions. It is shown that the phonon frequencies and their pressure dependences are related to macroscopic elastic parameters. More general, these results show that the measurement of Raman-active phonons provides a direct probe of bonding in metals, and agreement with theoretical models gives additional confidence in ab initio techniques.

Low-temperature high-pressure spectroscopy of lanthanum lutetium gallium garnet crystals doped withCr3+andNd3+

Low-temperature luminescence measurements under high pressures in diamond-anvil cell of nonstoichiometric lanthanum lutetium gallium garnet (LLGG) doped with Cr 3 + ions and nonintentionally with Nd 3 + ions are reported.Three nonequivalent Cr 3 + centers were found in the crystal using this technique. The results also reveal information about the electronic structure of different Cr 3 + centers in those crystals. Cr 3 + ions in a LLGG crystal experience a very low crystal field strength. The energy differences between the 4 T 2 and 2 E levels are negative, and equal to about - 1100 cm - for two of those centers and about -1500 cm - 1 for the third one. The spectral results were corroborated by a theoretical analysis of the luminescence decay times as a function of pressure, which allowed one to establish the exact values of the crystal-field parameter Dq at ambient pressure for those centers. The crystal exhibits a large inhomogeneous broadening of the R lines, associated with nonstoichiometry. In addition to the Cr 3 + luminescence also luminescence of Nd 3 + ions was detected in the LLGG crystals. One of the Nd 3 + luminescence lines, associated with the 4 F 3 / 2 4 I 9 / 2 transition. is strongly dependent on pressure, with a pressure coefficient equal to 0.96′0.02 cm - 1 /kbar, which makes this system interesting as a pressure gauge in the infrared region.

Applications of perforated diamond anvils for very high-pressure research

To reduce the large absorption effect in diamond anvil pressure cells for soft x rays, perforated anvils employed as diamond-backing plates (DBPs) used in conjunction with miniature anvils (MAs) made of 1/100 carat diamonds were tested for high-pressure efficacy. Static pressures beyond 100 GPa were generated using a piston/cylinder cell having 0.2 mm culets. Tests were carried out in 0.1 mm cavities drilled in a Re gasket, using Ar samples and ruby chips for manometry. Except for a single failure of a 0.3 mm culet MA, no damage was detected in the DBPs drilled with truncated conical holes tapering from 0.3 mm to 1, 1.5, and 2 mm diameter. Another arrangement in which one anvil was partially drilled leaving a 0.5 mm thick wall behind the culet achieved 100 GPa. Detailed discussions are given concerning the benefits of the DBP/MA cells for high-pressure studies with soft x rays and for background reduction in Raman, IR, UV, and 57Fe Mössbauer spectroscopies.

Investigation into the deformation of carbon nanotubes and their composites through the use of Raman spectroscopy

Abstract The deformation micromechanics of single-walled carbon nanotube (SWNT) and multi-walled carbon nanotube (MWNT) particulate nanocomposites has been studied using Raman spectroscopy. SWNTs prepared by two different methods (pulsed-laser and arc-discharge) and MWNTs have been used as reinforcement for a polymer matrix nanocomposite. The carbon nanotubes exhibit well-defined Raman peaks and Raman spectroscopy has been used to follow their deformation. SWNTs have been deformed with hydrostatic pressure in a diamond anvil pressure cell and has been found that the G′ peak position shifts to a higher wavenumber with hydrostatic compression. It has been found that for all nanocomposites samples deformed, the G′ Raman band shifts to a lower wavenumber upon application of a tensile stress indicating stress transfer from the matrix to the nanotubes and hence reinforcement by the nanotubes. The behaviour has been compared with that of high-modulus carbon fibres and has been modelled using orientation factors suggested initially by Cox. In this way it has been possible to demonstrate that the effective modulus of SWNTs dispersed in a composite could be over 1 TPa and that of the MWNTs about 0.3 TPa.

潤滑油の高圧物性とトライボロジー

Physical properties of lubricants under high pressure (e.g., density, elastic constant and viscosity) are the fundamental properties for the tribological evaluation (i.e. friction and wear) of rolling bearings, gears and traction drives. This paper introduces the importance of such physical properties of lubricants under high pressure in tribology and the application of a diamond-anvil pressure cell (DAC) for tribological measurements. A falling sphere viscometry in the DAC facilitated the viscosity measurements up to 2 GPa. A photon-correlation technique with laser light scattering in the DAC enabled the viscosity estimation of solidified glassy state lubricants (viscosity is about 109 Pa·s) from structural relaxation. Dynamic elastic moduli were obtained from Brillouin light scattering measurements in the DAC up to 4 GPa, which enabled the evaluation of the frequency dispersion of elastic moduli with quasi-static data.

Pressure Dependence of Cr3+ Fluorescence in θ-Alumina

The ruby fluorescence has, for many years, been used as a convenient tool for the determination of pressure in diamond-anvil cells. Subsequently, its use was extended to measure stresses in fibers and composites and, even more recently, the stresses in thermally grown oxide scales. This latter application has provided much needed, and technologically important, information on how and why scales debond from their parent alloy. Recent investigations of the early-stage oxidation of Al-containing superalloys18,19 report a transient “ruby-like” doublet (686.5 and 683.7 nm), which was assigned to the θ phase of Al2O3. The pesent work identifies that, as in ruby, Cr is the ion responsible for the fluorescence and also confirms that it stems from θ-Al2O3. The pressure dependence of the frequency of the θ-fluorescence, measured in a diamond-anvil cell, provides an additional tool for the characterization of stresses during early-stage oxidation. a Raman feature at 255 cm−1 is also identified as originating in θ-Al2O3. This feature is also likely to be useful in scale characterization.

Effect of pressure on the decay rate of 7Be

Beryllium-7 in Be(OH) 2 gel was compressed in diamond-anvil pressure cells up to 442 kbar at room temperature. By counting the activity of 7Be, the decay rate for the conversion of 7Be to 7Li via electron capture was measured. The decay constant of 7Be, λ, was found to increase, but the rate of increase decreased with increasing pressure. A quadratic regression of the data yields ( λ− λ 0)/ λ 0=(4.87×10 −5) P−(5.9×10 −8) P 2, where the subscript zero denotes zero pressure and P stands for pressure in kilobar. Thus, λ of 7Be increases by about 1% at 400 kbar. The observed data set can be rationalized by an increase in electron density near the nucleus of 7Be at high pressures. This result may bear some implications for the conversion of 40K to 40Ar, which has been widely adopted to date geological events.

Calorimetric Study of CeRu2Ge2 Under Continuously Swept Hydrostatic Pressure up to 8 GPa

We have implemented AC calorimetric measurements in diamond anvil pressure cells. The range of pressure (0–20 GPa), the excellent hydrostatic conditions of solid 4He used as the pressure transmitting medium associated with the possibility of continuously tuning the pressure at low temperature makes this experiment ideally suited for investigating phase diagrams under pressure and in particular for studying the thermodynamics of correlated metals around a Quantum Critical Point (QCP) where magnetic order is suppressed at absolute zero temperature. We present here results on the heavy fermion compound CeRu2Ge2 up to 8 GPa and down to 2 K. The specific heat anomalies associated with the different magnetic phase transitions are clearly resolved, allowing a precise determination of the magnetic phase diagram. On approaching the QCP close to 7 GPa, we observe a striking broadening of the antiferromagnetic transition associated with an anomalous behavior of the signal phase which could correspond to a change in the nature of this transition.

Magnetic neutron diffraction under pressures up to 43 GPa. Study of the EuX and GdX compounds

We present some recent results on magnetic neutron studies at pressures above 40 GPa. We used diamond and sapphire anvil pressure cells for low temperature neutron studies and a powder diffractometer specialized for high pressure studies. Focusing systems and low-background conditions allowed us to study samples with volumes as small as 0.001 mm3 in a diamond anvil cell at a pressure of 50 GPa. This technical progress allowed us to obtain new results in studies of “textbook” magnetic insulators EuX (X = S, Se, Te) and GdX (X = As, Sb, Bi). We found new magnetic phases. In the Eu-chalcogenides we observed a strong anion-dependent increase of the ferromagnetic exchange with decreasing lattice constant. In contrast, in the GdX compounds the antiferromagnetic order remains stable up to a pressure of 43 GPa. We show the importance of our results to understand the origin of indirect exchange interactions in magnetic semiconductors with well localized magnetic shells.

Inductive method for investigation of ferromagnetic properties of materials under pressure

A magnetic inductive method for investigating the magnetic properties of ferromagnetic substances over a broad range of temperatures under pressure in diamond-anvil cells is described. The proposed method exploits the fact that ferromagnetic substances change their dynamic magnetic susceptibility during magnetization by a constant external magnetic field up to the point of saturation. With increasing magnetic field, however, the magnetic properties of components of the high-pressure cell are essentially invariant. Therefore, the signal from the sample can be distinguished from that of the background caused asymmetries in the inductance system and the disposition of metal parts in the diamond-anvil cell. Measurements on CdCr2Se4 and iron demonstrate the feasibility of the method.

High pressure structure of (DIDCNQI) 2Cu

X-ray“monochromatic” Laue photo with diamond anvil pressure cell revealed c */3 satellite reflections indicating 2 k F CDW formation in the low dimensional compounds (DIDCNQI) 2Cu in the low pressure insulating(=I) phase around 11–20 kbar but no satellite reflections in the middle pressure metallic(=M) phases around 23–26 kbar.

Effect of pressure on phase transitions in K1−xNaxMnF3(x = 0.04)

The pressure-induced phase transition sequence in the title compound, potassium sodium fluoromanganate, has been investigated by single-crystal X-ray diffraction using synchrotron radiation and a diamond anvil pressure cell. Na^+ ions at 4% of the K^+ sites shift the ferrodistortive phase transition to the lower pressure P_{c1} of 2.75 (5) GPa compared to 3.12 GPa in the parent compound KMnF3. The transition is illustrated by the critical behaviour of the unit-cell dimensions, the pressure-dependent evolution of the MnF_6 ^- octahedral rotation and related macroscopic spontaneous strain. As far as precision of the present experiment allows, the observations show that the 4% of Na^+ admixture at the K^+ sites does not substantially change the nature of the transition at P_{c1}. The main effect of pressure is to stabilize the tetragonal phase II. The expected further evolution of the MnF_6 ^- octahedral tiltings, leading to the orthorhombic and monoclinic phases, has not been observed up to 8.33 GPa.

Fragility under pressure: Diamond anvil cell viscometry of ortho-terphenyl and salol

Viscosities of the fragile glass-forming liquids ortho-terphenyl and salol have been measured in a diamond anvil cell for pressures up to 1 GPa and for temperatures 300 K<T<425 K. Utilizing a rolling ball technique viscosities up to 108 mPas could be determined. From these data the pressure dependence of the fragility index, corresponding to a reference viscosity of about 108 mPas, has been calculated. For ortho-terphenyl it is found that this “low-viscosity” fragility index is pressure invariant within experimental error. Salol exhibits a more complicated behavior.

The Use of Quartz as an Internal Pressure Standard in High-Pressure Crystallography

The unit-cell parameters of quartz, SiO2, have been determined by single-crystal diffraction at 22 pressures to a maximum pressure of 8.9 GPa (at room temperature) with an average precision of 1 part in 9000. Pressure was determined by the measurement of the unit-cell volume of CaF2 fluorite included in the diamond-anvil pressure cell. The variation of quartz unit-cell parameters with pressure is described by: a −4.91300 (11) = −0.0468 (2) P + 0.00256 (7) P 2 − 0.000094 (6) P 3, c − 5.40482 (17) = − 0.03851 (2) P + 0.00305 (7) P 2 − 0.000121 (6) P 3, where P is in GPa and the cell parameters are in ångstroms. The volume–pressure data of quartz are described by a Birch–Murnaghan third-order equation of state with parameters V 0 = 112.981 (2) å3, K T0 = 37.12 (9) GPa and K′ = 5.99 (4). Refinement of K′′ in a fourth-order equation of state yielded a value not significantly different from the value implied by the third-order equation. The use of oriented quartz single crystals is proposed as an improved internal pressure standard for high-pressure single-crystal diffraction experiments in diamond-anvil cells. A measurement precision of 1 part in 10 000 in the volume of quartz leads to a precision in pressure measurement of 0.009 GPa at 9 GPa.

Compressibility and pressure dependence of charge transfer and Tc in pristine and iodine-intercalated single crystals of Bi 2.2Sr 1.8CaCu 2O 8+δ

Compressibility measurements for Bi 2.2Sr 1.8CaCu 2O 8+δ (Bi-2.2:1.8:1:2) and IBi 2.2Sr 1.8CaCu 2O 8+δ (IBi-2.2:1.8:1:2) single crystals were carried out in a diamond-anvil pressure cell up to 9 GPa. The values of bulk modulus are 68.56 and 48.21 GPa for Bi-2.2:1.8:1:2 and for IBi-2.2:1.8:1:2 single crystals, respectively. Hall coefficients and resistivities for oxygen annealed Bi-2.2:1.8:1:2 and I 0.7Bi-2.2:1.8:1:2 single crystals were measured under high pressure up to 1.5 GPa. The value of dR H dP for the oxygen annealed crystal is −0.06 × 10 −3 cm 3 C −1 GPa −1, which is one third of the as-grown crystal. The decrease of dR H dP after oxygen annealing is considered to be due to the increase of homogeneity of oxygen during high temperature annealing. The dR H dP of I 0.7 Bi-2.2:1.8:1:2 is −0.39×10 −3 cm 3 C −1 GPa −1 , which is nearly the same as that of IBi-2.2:1.8:1:2. That the negative dR H dP of intercalated crystals is nearly twice as large as that of pristine crystals is concerned with the deposition of the iodine molecular state under pressure. The T c of oxygen-annealed Bi-2.2:1.8:1:2 increases with increasing pressure at a parabolic curve below 1.5 GPa. By using the Gupta model, we simulated T c( P) up to 6 GPa, and found that the maximum value of T c( P) is 88 K at P = 4.1 GPa. This is in good agreement with the experimental result measured by Klotz et al. [Physica C 209 (1993) 499]. The T c of the I 0.7Bi-2.2:1.8:1:2 crystal increased linearly at a rate of dT c dP = −3.6 K/ Gpa . This is the opposite of the behaviour of IBi-2.2:1.8:1:2 which decreased linearly at a rate of dT c dP = −3.6 K/GPa , although both intercalated crystals are overdoped compounds.