High-pressure Diamond Anvil Cell Research Articles

Shadowing and absorption corrections of high-pressure powder diffraction data: toward accurate electron-density determinations.

The shadowing of the primary beam and of reflections from a powder crystal sample enclosed in a diamond-anvil high-pressure cell (DAC) is described for unrestricted data-collection procedures. The corrections account for the shadowing of the data measured with point- or area-detector diffractometers and can be applied for any containers of environment devices enclosing a powdered sample. The general procedure for correcting the powder diffraction data can be applied for analysing and optimizing diffractometric procedures of data collection and provides facilities for collecting high-pressure powder diffraction data with the DAC positioned optimally and rotated to counteract the preferred-orientation and particle-size effects, and to increase the resolution of data. The quadrature effects of numerical integration for the accuracy of computed corrections have been analysed.

Shadowing and absorption corrections of single-crystal high-pressure data

Abstract The effect of shadowing the sample crystal enclosed in the diamond-anvil high-pressure cell (DAC) by the gasket edges, i.e. by the walls of the high-pressure chamber, has been described for unrestricted data-collection procedures. A general vector formalism reveals new features of the shadowing and absorption corrections, depending on the primary beam-DAC-reflection configuration. The corrections apply to the data measured with conventional normal-beam-equatorial diffractometers, or with area-detectors. The simple vector approach optimizes computations and affords straightforward corrections of intensities. Feasibility of enhancing the resolution of numerical integration by applying fine grid divisions, has been discussed.

Shear waves in the diamond-anvil cell reveal pressure-induced instability in (Mg,Fe)O.

The emerging picture of Earth's deep interior from seismic tomography indicates more complexity than previously thought. The presence of lateral anisotropy and heterogeneity in Earth's mantle highlights the need for fully anisotropic elasticity data from mineral physics. A breakthrough in high-frequency (gigahertz) ultrasound has resulted in transmission of pure-mode elastic shear waves into a high-pressure diamond-anvil cell using a P-to-S elastic-wave conversion. The full elastic tensor (c(ij)) of high-pressure minerals or metals can be measured at extreme conditions without optical constraints. Here we report the effects of pressure and composition on shear-wave velocities in the major lower-mantle oxide, magnesiowüstite-(Mg,Fe)O. Magnesiowüstite containing more than approximately 50% iron exhibits pressure-induced c(44) shear-mode softening, indicating an instability in the rocksalt structure. The oxide closer to expected lower-mantle compositions ( approximately 20% iron) shows increasing shear velocities more similar to MgO, indicating that it also should have a wide pressure-stability field. A complete sign reversal in the c(44) pressure derivative points to a change in the topology of the (Mg,Fe)O phase diagram at approximately 50-60% iron. The relative stability of Mg-rich (Mg,Fe)O and the strong compositional dependence of shear-wave velocities (and partial differential c(44)/ partial differential P) in (Mg,Fe)O implies that seismic heterogeneity in Earth's lower mantle may result from compositional variations rather than phase changes in (Mg,Fe)O.

High-pressure phase transformation of silicon nitride

We provide evidence for a high-pressure phase transformation (HPPT) in the ceramic material silicon nitride. This HPPT is inferred by a high-pressure diamond anvil cell, Raman spectroscopy, scanning/transmission electron microscopy, and optical and acoustic microscope inspection. In the case of silicon nitride, the HPPT involves a ductile or metallike behavior that is observed in severe deformation processes, such as nanoindentation and micromachining. This pressure-induced plasticity is believed to be similar to that found in silicon and germanium with its origin in the high-pressure metallic β-Sn phase formation.

Refinement of the crystal structure of Sb-I, at 2.22 GPa

Sb, trigonal, R3m (No. 166), a = 4.2687(2) A, c = 10.9244(6) A, V = 172.4 Â, Z = 6, R(P) = 0.066, R(I) = 0.059, 7 = 295 K, Ρ = 2.22 GPa. Discussion Structural parameters of antimony at elevated pressures up to 8.5 GPa were determined earlier by means of single crystal X-ray diffraction in diamond anvil cells [1], We re-refined the parameter values in order to gain a quantitative measure for the reliability of full profile refinements using powder patterns measured with synchrotron radiation. The result of the least squares procedure is within three standard deviations identical to the values obtained by single crystal diffraction methods (z = 0.2358(6) at Ρ = 1.5 GPa and ζ = 0.2379(6) at Ρ = 2.66 GPa [ 1 ]) . The resulting interatomic distances of 3 χ 2.895(1) A and 3 χ 3.253(1) Â support the finding that the rhombohedral low-pressure phase approaches a simple cubic arrangement with increasing pressures [1,2]. Table 1. Data collection and handling. Powder: black, size 5 -10/ Angle-dispersive X-ray powder diffraction experiments were performed on ID-9 at ESRF using an image plate detector. The powdered particles were placed in a gasketed diamond anvil high-pressure cell using a small sphere of ruby for pressure calibration and a 4:1 mixture of ethanol and methanol as a pres- sure transmitting medium. Table 2. Atomic coordinates and displacement parameters (in Â).

On compressibility of osmium metal

On the basis of the high-pressure diamond anvil cell experiments on Os metal, Cynn et al. [Phys. Rev. Lett. 88, 135701-1 (2002)] have reported that this metal has lower compressibility than diamond. In the present work we have reanalysed the experimental data of Cynn et al. We find that the bulk moduli of Os and diamond are close to each other, implying that Os metal is as incompressible as diamond, but not more so. Our first principles total energy calculations using the full potential linearised augmented plane wave method on Os and diamond also suggest the same results.

Amorphous boron gasket in diamond anvil cell research

Recent advances in high-pressure diamond anvil cell experiments include high-energy synchrotron x-ray techniques as well as new cell designs and gasketing procedures. The success of high-pressure experiments usually depends on a well-prepared sample, in which the gasket plays an important role. Various gasket materials such as diamond, beryllium, rhenium, and stainless steel have been used. Here we introduce amorphous boron as another gasket material in high-pressure diamond anvil cell experiments. We have applied the boron gasket for laser-heating x-ray diffraction, radial x-ray diffraction, nuclear resonant inelastic x-ray scattering, and inelastic x-ray scattering. The high shear strength of the amorphous boron maximizes the thickness of the sample chamber and increases the pressure homogeneity, improving the quality of high-pressure data. Use of amorphous boron avoids unwanted x-ray diffraction peaks and reduces the absorption of incident and x rays exiting the gasket material. The high quality of the diffraction patterns makes it possible to refine the cell parameters with powder x-ray diffraction data under high pressure and high temperature. The reactivity of boron prevents its use at high temperatures, however. When heated, boron may also react with the specimen to produce unwanted phases. The relatively porous boron starting material at ambient conditions also poses some challenges for sample preparation.

Pressure dependence of phonons and excitons in InSe films prepared by metal-organic chemical vapor deposition

The pressure dependence of the Raman spectra of phase-pure InSe thin films prepared by the low-pressure metal-organic chemical vapor deposition technique has been studied using a diamond-anvil high-pressure cell. Enhancement in the intensities of the Raman modes has been observed as a result of pressure-induced ``tuning'' of the energy of the ${M}_{1}$-type hyperbolic exciton in InSe at $\ensuremath{\sim}2.54\mathrm{eV}$ through discrete incident laser photon energies. The pressure coefficients of the phonon modes and of the hyperbolic exciton in InSe have been determined.

Pressure-induced phase transitions of piezoelectric single crystals from the langasite family: La3Nb0.5Ga5.5O14 and La3Ta0.5Ga5.5O14.

The hydrostatic compression of piezoelectric single crystals of La(3)Nb(0.5)Ga(5.5)O(14) (LNG) and La(3)Ta(0.5)Ga(5.5)O(14) (LTG) was studied at pressures of up to 23 GPa in diamond-anvil high-pressure cells using single-crystal X-ray diffraction techniques. The reflection-intensity data for LNG and LTG were collected at pressures of up to 22.8 GPa and 16.7 GPa, respectively. Both compounds show anisotropic behaviour under pressure, which is caused by differences in bonding parallel to the a and c directions. The compression of strongly rigid structures leads to increasing internal strains and results, at pressures of 12.4 (3) GPa for LNG and 11.7 (3) GPa for LTG, in a transition to lower symmetry. The compressibilities along the c axis are almost the same for LNG and LTG through the whole investigated pressure range. In contrast, the pressure dependencies of the a axis of these materials are similar only for the initial phase, and the axial compressibilities for the high-pressure polymorphs of LNG and LTG are significantly different to each other. The volume compressibilities of trigonal LNG and LTG (space group P321) are about 0.007 GPa(-1); respective bulk moduli are 145 (3) GPa and 144 (2) GPa. The monoclinic high-pressure phases (space group A2) of LNG and LTG show differing compressions, which can be explained by the substitution of Ta(5+) for Nb(5+). Thus, the bulk moduli for the high-pressure polymorphs of LNG and LTG are B(0) = 93 (2) GPa and B(0) = 128 (12) GPa, respectively. The volume compressibilities of the high-pressure phases at 0.011 GPa(-1) for LNG and 0.008 GPa(-1) for LTG are higher than the initial phases, this effect being more pronounced in the case of LNG.

Pressure-dependent Fourier transform infrared spectroscopy of a poly (ester urethane)

The effects of hydrostatic pressure upon (1) a segmented poly (ester urethane), (2) a hydrolytically degraded sample of the same polymer, and (3) models for the polyurethane and polyester segments in this polymer have been studied by Fourier transform infrared spectroscopy using high-pressure diamond anvil cells (DACs). The pressure responses of the vibrational frequencies of specific functional groups of the poly (ester urethane) in the 0–100-kbar range are compared with data for individual segment models and the partially degraded sample. The results indicated that the polymer is highly stable in this pressure regime, with no measurable degradation or phase changes. Differences in the pressure dependency of specific infrared bands between the poly (ester urethane) sample and the partially degraded sample are slight and consistent with changes in hydrogen-bonding interactions and shorter chain lengths in the degraded sample.

Influence of high hydrostatic pressure on lattice parameters of a single crystal of La3Nb0.5Ga5.5O14

Abstract Unit-cell parameters of La3Nb0.5Ga5.5O14 (langanite) have been determined at a number of pressures up to 23GPa in diamond anvil high pressure cells with single crystal X-ray diffraction techniques. The anisotropic behaviour of unit cell parameters of langanite is caused by differences of bonding strength in direction parallel to the a- and c-axis. Within the investigated pressure range, the c/a-ratio increases from 0.6232 to 0.6503. The volume compressibility of trigonal langanite (space group P321) is the 0.007 GPa-1, with calculated bulk modulus of 145(3)GPa (B'0=1.4(8)). At a pressure of 12.4(3)GPa a first-order phase transition was detected, characterised by a discontinuity in the pressure dependence of lattice parameter c. The high-pressure phase (presumably monoclinic, A2) with a volume compressibility of 0.011 GPa-1 (B0=93(2) GPa, B'0=1.9(9)) is more compressible as compared to the initial phase due to an abnormal pressure dependence of lattice parameter a.

Pressure Dependence of Raman Modes in the Chalcopyrite Quaternary Alloy AgxCu1xGaS2

Raman scattering in the chalcopyrite quaternary alloy Ag{sub x}Cu{sub 1-x}GaS{sub 2} has been studied under high pressure (up to 7 GPa) and at low temperature (50 K) using a diamond anvil high pressure cell for alloy concentrations x=1, 0.75, 0.5, 0.25 and 0. This has allowed us to determine the dependence of their zone-center phonon modes on both pressure and alloy concentration. The resultant phonon pressure coefficients are helpful in understanding the nature of the phonon modes in these chalcopyrites.

Pressure Dependence of Raman Modes in the Chalcopyrite Quaternary Alloy AgxCu1?xGaS2

Raman scattering in the chalcopyrite quaternary alloy Ag{sub x}Cu{sub 1-x}GaS{sub 2} has been studied under high pressure (up to 7 GPa) and at low temperature (50 K) using a diamond anvil high pressure cell for alloy concentrations x=1, 0.75, 0.5, 0.25 and 0. This has allowed us to determine the dependence of their zone-center phonon modes on both pressure and alloy concentration. The resultant phonon pressure coefficients are helpful in understanding the nature of the phonon modes in these chalcopyrites.

Evaluation of High Viscosity of Solidified Lubricants at High Pressure by Rayleigh Light Scattering and Photon Correlation Technique.

A new viscosity measuring system was designed and set up employing Rayleigh light scattering and the photon correlation technique in which a high-pressure diamond-anvil cell (DAC) was used. Two kinds of experiments were conducted. One was the measurement of a dilute suspension of polystyrene latex spheres in liquid lubricant and W/O emulsion. Correlation functions induced by the Brownian motion of fine spheres in the lubricant were observed and the viscosities were obtained, the measurement time of which was one-tenth shorter than that of the falling-body method. The other experiment was the measurement of 5P4E (polyphenyl ether) and DOP (dioctylphthalate) without mixing polystyrene spheres. Very weak but observable correlation functions related to structural relaxation were observed and the viscosities of solidified lubricants (about 10 9 Pa.s), obtained in a very short time by introducing a shift factor for relaxation time, were consistent with those extrapolated from data obtained using the falling-body method.

Dependence of High Pressure on Phase Transformation in Zr<SUB><B>41.2</B></SUB>Ti<SUB><B>13.8</B></SUB>Cu<SUB><B>12.5</B></SUB>Ni<SUB><B>10</B></SUB>Be<SUB><B>22.5</B></SUB>

The phase transformation of Zr 41.2 Ti 13.8 Cu 12.5 Ni 10 Be 22.5 bulk metallic glass (BMG), which arises from compression and decompression, has been investigated by using cubic type high-pressure apparatus and Diamond Anvil Cell (DAC). The temperature of phase transformation from the amorphous to the crystalline (T x ) displays a universal decrease under high pressure. Based on the observation of in-situ resistance measurement in a DAC, 24 gigapascals (GPa) was able to lead to the crystallization event of this BMG at room temperature. The dependence of T x on pressure (P) followed the relation of T x = 714.3 - 7.97P - 0.399 P 2 . Moreover, an unexpected new phenomenon emerged has also been found during decompression. The high pressure induced crystalline phase reverted back to the amorphous state during downloading, which was further confirmed by TEM.

Measuring Speed of Sound and Thermal Diffusivity in the Diamond-Anvil Cell

Transient grating spectroscopy in the diamond-anvil high-pressure cell permits, in favorable cases, determination of the equation of state and thermal transport properties of fluids at high temperatures and pressures. Measurements of the speed of sound and thermodynamic properties of aqueous Na2SO4to 3.4 GPa at 300°C and the thermal diffusivity of oxygen are reported as examples of the application of this technique.

Electrical Properties of an Organic Conductor, β′- (BEDT-TTF)2ICl2 up to 10 Gpa

Abstract Four-probe resistivity measurements were made on an organic semiconductor, β′-(BEDT-TTF)2ICl2 up to 10 Gpa by using a diamond anvil high-pressure cell. The activation energy was decreased with increasing pressure and the metallic phase appeared around 8 Gpa. When the pressure was kept around 10 Gpa, the resistivity was gradually increased with time, indicating an irreversible pressure-induced solid state transformation.

Nanoindentation of Pressure Quenched Fullerenes and Zirconium Metal from a Diamond Anvil Cell

ABSTRACTThe sample size employed in high pressure diamond anvil cells is limited to a diameter of typically 25 to 150 microns. While this size is often sufficient for diagnostics using synchrotron x-ray diffraction and Raman scattering, ex-situ measurements of mechanical properties using conventional microhardness indentation techniques is not feasible. For some materials, the high pressure phase(s) can be quenched to ambient pressure allowing further characterization by other techniques. We make use of the very small probe volume allowed by nanoindentation to investigate the pressure-quenched structures of both C70 fullerene and zirconium. For the case of C70, we show that the amorphous phase established above 35 GPa can be quenched to ambient, and that it shows a largely elastic indentation loading behavior with a hardness of 30 GPa. We establish that this hard carbon phase contains a mixture of sp2- and sp3-bonded carbon and that it can be produced from C70 fullerene by application of pressure at room temperature. With regard to zirconium metal, we confirm the irreversible transformation from the ambient hexagonal-close-packed phase to the simple hexagonal Ω-phase (AlB2 structure) and document an 80% increase in hardness that may be attributed to the presence of covalent bonding based on sd2-hybridized orbitals forming graphite-like nets in the (0001) plane of the AlB2 structure.

Applications of impulsive stimulated scattering in the Earth and planetary sciences.

The elastic, thermodynamic, and transport properties of crystals and fluids at high temperature and pressure play a central role in the earth and planetary sciences as well as in a variety of technologies. These properties also constitute a principal experimental constraint on the description of intermolecular interactions at short distances. Aspects of "impulsive stimulated scattering," when adapted to measurements in the diamond-anvil high-pressure cell, provide an approach to the determination of a subset of equilibrium and dynamic properties at high density.

Diffractometric crystal centering

A general formalism for centering a single-crystal on a four-circle diffractometer, based on the setting angles of reflections, is presented. The minimum information for the determination of crystal displacement are the diffractometer setting angles of two reciprocal vectors. The method is independent of the crystallographic system and does not require prior information about the crystal lattice. The size of the radiation source, beam divergence and homogeneity are shown to be significant factors for calculating the crystal displacement from the positions of the reflections. The method is primarily designed for samples enclosed in high-pressure diamond-anvil cells and other environments obscuring visual control of the sample position; however, high accuracy of the method in most cases allows the optical centering of the crystals to be improved, particularly for irregularly shaped samples. A procedure for retrieving true lattice dimensions, by accounting for the effect of the crystal displacement from the diffractometer center, is also presented.