Pressure In Diamond Anvil Cell Research Articles

A mineralogical Raman spectroscopy study on eclogitic garnet inclusions in diamonds from Argyle

In an attempt to better define the depths of formation of eclogitic-paragenesis diamonds from the Argyle lamproite pipe, we have employed a Laser Raman microprobe to determine the Raman peak shift of a garnet inclusion (extracted from diamond) with pressure in a diamond-anvil pressure cell. On the basis of these data, we further found that the in situ garnet inclusions record near-atmospheric pressures within the limits of experimental uncertainty. Data on the compressibility and thermal expansivity of both diamond and garnet were used to define a P-T curve for the entrapment of garnet in diamond. A window within the range 47 kbar at 1100° C (150 km) to 93 kbar at 1500° C (280 km) for the formation of syngenetic garnet inclusions in diamond is defined by the intersection of the continental geotherm with the diamond-graphite boundary and the entrapment curve determined in the present study. This P-T window is consistent with the constraints imposed by other petrological studies of co-existing inclusions. Most of eclogitic-paragenesis diamonds from Argyle are estimated to have formed at a depth less than 250 km, if temperature estimates from petrological study are used.

Isothermal phase behavior of Ag 3SbS 3, ZnGeP 2, and ZnS

The isothermal phase behaviors of Ag 3SbS 3, ZnGeP 2, and ZnS have been determined as a function of pressure at room temperature. Phase transformations were observed optically for each material in a diamond anvil cell with single crystals at pressures of (4.9±0.15) GPa, (20±5) GPa, and (15.0±0.2) GPa, respectively. ZnGeP 2 also transformed to a second high-pressure phase at approximately 32 GPa. Under hydrostatic pressure zinc sulfide showed no transformation between the wurtzite and sphalerite forms. The pressure-volume relations were measured in the diamond anvil pressure cell by the energy dispersive X-ray diffraction method. The resulting data were analyzed for each low-pressure phase in terms of model equations of state, including the Birch, Birch-Murnaghan, Murnaghan, and Tait equations. The isothermal bulk modulus, B, was determined in each case with the estimated values being: 80 GPa for ZnS (wurtzite); 67 GPa for ZnS (sphalerite); 28 GPa for Ag 3SbS 3; and 79 GPa for ZnGeP 2. Estimates were also made for the pressure derivative, (d B/d P), at zero pressure, with the values being: 3.7, 4.8, 5.6, and 3.2, respectively.

Pressure-volume-temperature behavior and heterogeneous equilibria of the non-quenchable body-centered tetragonal polymorph of metallic tin †

Forty molar volume determinations for the high-pressure phase of metallic tin, Sn(bct), measured by energy-dispersive X-ray diffraction in a heated diamond-anvil pressure cell, form the basis for the first experimentally-determined P-V-T equation of state for any non-quenchable phase. The resulting isochores for Sn(bct) are concave towards the pressure axis; their slope varies from approx. 120 deg GPa −1 at the Sn(β)-Sn(melt) triple point at 308°C and 2.9 GPa, to approx. 290 deg GPa −1 at the room temperature Sn(β)-Sn(bct) transition at 9.4 GPa. Used in conjunction with the P-V-T data for Sn(β) from Cavaleri et al., J. Phys. Chem. Solids 49, 945 (1988) [1], these Sn(bct) volume measurements reveal that Δ V for the Sn(β)-Sn(bct) reaction remains essentially constant at approx. −0.135 J MPa −1 mol −1 whereas Δ S increases from +2.15 J deg −1 mol −1 at room temperature to +7.15J deg −1 mol −1 at the triple point. The molar volume and entropy of Sn(melt) at the triple point were determined to be 16.113 J MPa −1mol −1 and 81.91J deg −1mol −1, respectively, indicating that ΔS along the Sn(β) melt curve remains very nearly constant whereas Δ V decreases by approx. 31% from room pressure to the triple point.

A pressure-volume-temperature equation of state for Sn(β) by energy dispersive X-ray diffraction in a heated diamond-anvil cell

A total of 36 molar volume determinations measured by energy-dispersive X-ray diffraction in a heated diamond-anvil pressure cell form the basis for a P-V-T equation of state for Sn(β). Isothermal Murnaghan regressions for the 25, 100, 160, and 225°C subsets of these data yield −1.38 (±0.13) × 10 −2GPa degree −1 for ( ∂K ∂T ) 00. The slopes of the Sn(β) isochores increase from approx. 235° GPa −1 at room pressure and temperature to 260° GPa −1 at the Sn triple point to 370° GPa −1 at the room temperature Sn(β)-Sn(bct) transition at 9.4 GPa, indicating that the product α P K T decreases with decreasing volume by more than 35% of its initial value. The a crystallographic direction is significantly less compressible and slightly less expandable than c; the extent of this anisotropic behavior decreases at simultaneously elevated pressure and temperature. A five-parameter temperature-corrected Murnaghan equation fits the entire data set well within the experimental error. This explicit V( T, P) equation is used to integrate literature heat capacity data to elevated pressure, yielding entropies and Gibbs energies for all pressures and temperatures within the Sn(β) stability field.

High‐Pressure Phase Transitions in Zirconia and Yttria‐Doped Zirconia

Raman spectroscopy has been utilized to characterize the phase transformations and transition pressures in pure and doped zirconia containing 3, 4, and 5 wt% Y2O3. The pressure‐induced transformations were investigated to over 6 GPa (at room temperature) using a diamond anvil pressure cell. Pure zirconia single‐crystal samples transformed to a “new” tetragonal phase (different from the one obtained at high temperatures at atmospheric pressure) at about 4 GPa. The pressure transformation, like the temperature transition, was reversible and exhibited an approximately 0.45‐GPa hysteresis at room temperature. The 3 and 4 wt% Y2O3 crystals underwent a monoclinic (P21/b) to tetragonal (P42 nmc) phase transition similar to that observed at high temperatures. This phase change was found to be irreversible on releasing the pressure. The 5 wt% Y2O3 at atmospheric pressure consists of a tetragonal modification in a disordered cubic matrix; a gradual, but reversible, disordering transformation of the tetragonal precipitate takes place with pressure.

Experimental studies at Karlsruhe and Oak Ridge of transplutonium metals and compounds under pressure

At Karlsruhe, the structural behavior of the first four transplutonium metals and two Bk-Cf alloys has been studied as a function of pressure in diamond anvil cells using X-ray diffraction. The sequence of structures exhibited as pressure is increased is d.h.c.p. → c.c.p. → orthorhombic. In addition a distorted c.c.p. phase is observed in americium, Bk 0.40Cf 0.60 and californium between the c.c.p. and orthorhombic phases. The volume collapse and transformation to the lower symmetry orthorhombic structure are indicative of the onset of delocalization of the 5f electrons in these materials. The highest delocalization pressure and largest volume collapse occur in curium metal, reflecting its stable half-filled 5f 7 electron configuration. Diamond anvil cells have also been used at Oak Ridge to contain AmI 3, CfBr 3 and CfCl 3 under pressure for investigation by absorption spectro-photometry. Both AmI 3 and CfBr 3 exhibit pressure-induced, irreversible phase transformations to the PuBr 3-type orthorhombic structure, a denser form of these compounds. Thus the driving force for these transformations is more efficient crystal packing. Both hexagonal (to 22 GPa) and orthorhombic (to 35 GPa) CfCl 3 exhibit only reversible spectral changes with pressure. This probably reflects their nearly identical room temperature and pressure (RTF) unit cell volumes. In both cases the spectra obtained are consistent with a continuous alteration of the RTF structure with pressure; physical compression seems to make a given f → f transition easier. Additional data are being sought to elucidate more completely the behavior of CfCl 3 under pressure.

Effect of pressure on the crystal structure of perovskite-type MgSiO3

The crystal structure of perovskite-type MgSiO3 has been studied up to 96 kbar, using a miniature diamondanvil pressure cell and by means of single-crystal four-circle diffractometry. The observed unit cell compression gives a bulk modulus of Ko=2.47 Mbar, assuming K′o=4. The unit cell compression is controlled mainly by the tilting of SiO6 octahedra. The effect of pressure is to change Mg polyhedron towards 8-fold coordination rather than 12-fold coordination. The polyhedral bulk moduli of SiO6 and MgO8 are 3.8 Mbar and 1.9 Mbar, respectively.

Mössbauer effect of europium metal under pressure

The pressure dependence of the magnetic hyperfine field and of the isomer shift of 151Eu in europium metal has been studied in a diamond anvil pressure cell at low temperatures. In the pressure range 0–12 GPa at 44 K the magnetic hyperfine field changes from −22 to −8 T while the isomer shift increases from −7.3 to −3.8 mm s−1 relative to a SmF3 source. The changes are interpreted as indicative of a pressure-driven intermediate valence state causing a reduced magnetic moment in Eu. Intermediate valence and magnetic order coexist over the range of pressures studied.

Pressure dependence of the lowest direct absorption edge of ZnTe

The dependence of the lowest direct absorption gap E 0 of ZnTe on hydrostatic pressure has been measured at room temperature with a diamond anvil cell for pressures up to the second phase transition (11.9 ± 0.3 GPa). The energy gap E 0 (eV) = 2.27 + 10.4 · 10 -2 · P − 28 · 10 -4 · P 2 (P in GPa) exhibits a sublinear dependence on P up to the first phase transition at 9.4 + 0.3 GPa. However, if the gap is plotted as a function of the relative change of lattice constant (-Δa/a 0) it shows, within error, a linearity with E 0 (eV) = 2.266 + 16.2 (-Δa/a 0). The experimental results are compared to theoretical calculations based on a local empirical pseudopotential and with recently published ab initio LMTO calculations.

High-pressure phase transformations and isothermal compression in CaTiO 3 (perovskite)

A polycrystalline CaTiO 3 (perovskite) was investigated under static pressures up to 38 GPa and temperatures up to 1000°C by using a diamond anvil pressure cell, a YAG laser, and the ruby fluorescence pressure calibration system. In situ x-ray diffraction data reveal that at room temperature, the orthorhombic CaTiO 3(I) transforms into a hexagonal CaTiO 3(II) at ∼ 10 GPa with a volume of change of 1.6%. At 1000°C, the orthorhombic CaTiO 3(I) first transforms into a tetragonal CaTiO 3(III) at 8.5 GPa and then transforms further into a hexagonal CaTiO 3(II′) at ∼ 15 GPa with molar volume changes of 0% and 1.6%, respectively. All three high-pressure polymorphs found in this study are nonquenchable. Isothermal compressibility of the orthorhombic CaTiO 3 was derived from measurements under truly hydrostatic environments (i.e., ⩽ 10.4 GPa). By assuming K ′ 0 = 5.6 obtained ultrasonically on SrTiO 3 perovskite, the value of the bulk modulus ( K 0) was calculated with the Birch-Murnaghan equation to be 210 ± 7 GPa.

In situ determination of crystal structure for high pressure phase of ZrO2 using a diamond anvil and single crystal X-ray diffraction method

Combining a miniature diamond-anvil pressure cell with a single crystal four-circle diffractometer, the crystal structure of a synthetic ZrO2 has been studied in situ up to 51 kbar at room temperature. The space group of the unquenchable orthorhombic high pressure phase is Pbcm. The directions of the b and c axes are preserved through the transition and the transformation is displacive. The coordination configurations of the Zr atoms and oxygen atoms are the same in the high pressure and low pressure phases. The orthorhombic high pressure phase has a higher entropy than that of low pressure monoclinic phase.

Energy dispersive spectroscopy using synchrotron radiation: Intensity considerations

Detailed considerations are given to the reliability of energy dependent integrated intensity data collected from the pressure cavity of a diamond-anvil pressure cell illuminated with heterochromatic radiation from a synchrotron storage ring. It is demonstrated that, at least in one run, the electron beam current cannot be used to correct for energy-intensity variations of the incident beam. Rather, there appears to be an additional linear relationship between the decay of the synchrotron beam and the magnitude of the background intensity.

Phase transformations in serpentine at high pressures and temperatures and implications for subducting lithosphere

Serpentine may be regarded as a hydrous form of a 1:1 (molecular) mixture of olivine and pyroxene, or a simplified hydrous ‘pyrolite’ upper mantle composition. The phase behaviour of two natural serpentines, having the approximate compositions of (Mg 0.99Fe 0.01) 3Si 2O 5(OH) 4 and (Mg 0.91Fe 0.09) 3Si 2O 5(OH) 4, was investigated between 60 and 280 kbar (inclusive) at 700 ∼ 1000°C in a diamond-anvil pressure cell coupled with laser heating. By incorporating earlier work, the results suggest that at pressures greater than 30 kbar and temperatures in the range 600 – 1000°C serpentine displays the following sequence of phase transformations with increasing pressure: serpentine 40–60 kb forsterite + talc + water 70–80 kbforsterite + orthoenstatite + water 100 kg forsterite + clinoenstatite + water 120 kb clinoenstatite + phase A + water 130 kb stishovite + phase A + brucite 180 kg stishovite + phase B + brucite 220 kb ?? None of the high-pressure phases expected in olivine and pyroxene, such as the spinel modification of olivine, the ilmenite and perovskite modifications of pyroxene, was observed in serpentine up to about 280 kbar loading pressure. On the basis of these results, the effect of H 2O on phase transformations of olivine and pyroxene at high pressures and high temperatures has been deduced. It has been found that the modified spinel phase of Mg 2SiO 4 does not occur in the system having a 1:1 mixture of forsterite and enstatite and containing more than about 4 wt.% H 2O. The spinel phase of Mg 2SiO 4 does not appear at its equilibrium transition boundary (modified spinel ↔ spinel) in the same system containing more than about 3 wt.% H 2O. Thus, if more than about 4 wt.% H 2O is present in the middle portion of a subducting lithosphere, the so-called 400-km seismic discontinuity observed in the normal mantle may not take place in the downgoing slabs. Where these transitions do occur at a low H 2O content, the associated change in density and, accordingly, the magnitude of discontinuities in the seismic wave velocities, would be reduced by a factor of 2–3 if 2 wt.% H 2O is present in the system.

Measurement and calculation of the pressure dependence of the Mössbauer isomer shift of metallic 119Sn for the pressure range 0

We have measured the pressure dependence of the M\"ossbauer isomer shift S(P) for tin for the pressure range 0\ensuremath{\le}P\ensuremath{\le}310 kbar through the use of a diamond anvil pressure cell. Also, S(P) has been calculated for this pressure range using a relativistic augmented-plane-wave model. In these calculations, a Kohn-Sham, a Hedin-Lundqvist, or a Slater model was used to describe the electron-electron interaction. A Dirac-Hartree-Wigner-Seitz model was used to calculate the muffin-tin potential. For the 92-kbar phase transition, the calculated change of the electron density at the tin nucleus was found to be roughly independent of whichever of the above models was used to describe the electron many-body interaction. Based on this, a value for the M\"ossbauer isomer-shift calibration constant of 0.072${a}_{0}^{3}$ mm/sec, and an approximate description of the measured S(P) for the above pressure range is obtained. A comparison of our results with other measurements and calculations is made.

Compression and polymorphism of potassium to 400 kbar

Both the compression and polymorphism of K were investigated to about 400 kbar at room temperature in a diamond-anvil pressure cell by optical and X-ray diffraction techniques. The ambient b.c.c.-K(I) is stable to about 120 kbar. The compression data for K(I), fitted to the Birch equation of state, yielded the zero-pressure bulk modulus B 0 = 29.9 ± 0.2 kbar and its first pressure derivative B' 0 = 4.15 ± 0.10. These values agree very well with those of recent data derived from the direct measurement of length changes using piston-displacement (to 20 kbar) and laser interferometer (to 7 kbar) techniques. On the basis of the compression data for K(I) alone, Bridgman's pressure scale may be overestimated by about 10 kbar at 100 kbar and that of Kennedy and LaMori may be underestimated by about 5 kbar at 50 kbar. Two high-pressure polymorphs of K were revealed in the pressure range 100–200 kbar. The b.c.c. → f.c.c. transition in K was observed to occur near 120 kbar, accompanied by a −2.5% discontinuous change in volume. The sample changes gradually from silver to gold in the range 130–150 kbar. The f.c.c.-K.(II) transforms further into an as yet undetermined structure between 170 and 190 kbar. No change in colour was observed in the latter transition. K(III) is stable up to at least about 400 kbar. The equation of state for the f.c.c. phase of K cannot be established. The volume of K was compressed more than 60% in the vicinity of 200 kbar, however.

Compression studies of a nickel-based superalloy, MAR-M200, and of Ni3Al

The lattice parameter of a cubic nickel-based alloy, MAR-M200, has been determined as a function of pressure for 0<p<14 GPa at room temperature. A similar study was made for Ni3Al in the range 0<p<11 GPa at room temperature. In both cases, the diamond anvil pressure cell was used in conjunction with the energy dispersive method of x-ray diffraction. The data were analyzed in the context of model equations of state and in comparison with other results from ultrasonic studies.

Pressure dependence of the lowest direct absorption edge of ZnSe

The variation of the lowest direct absorption edge (E 0) of ZnSe with hydrostatic pressure has been measured at room temperature with a diamond anvil cell for pressures up to the phase transition (13.5±0.2 GPa). The gap varies sublinearly with pressure. However, when the gap is plotted as a function of the relative change of the lattice constant (-Δa/a 0) it shows a slight supralinearly in contrast to most III–V tetrahedral semiconductors which retain a slight sublinearly even as a function of (-Δa/a 0). The experimental results are compared to theoretical calculations based (a) on the local density approximation combined with the self-consistent band calculations using the LMTO method (LD-LMTO) and (b) on a local empirical pseudopotential. Both calculations predict a sublinear dependence of E 0 as a function of (-Δa/a 0). The semiempirical Murnaghan's equation of state that was calculated with the LD-LMTO method, has also been tested by determining the lattice constant under pressure with an energy dispersive x-ray diffractometer.

Pressure‐Temperature Phase Diagram of Zirconia

The pressure‐temperature phase diagram of zirconia was determined by optical microscopy and X‐ray diffraction techniques using a diamond anvil pressure cell. At room temperature, monoclinic ZrO2 transforms to a tetragonal phase (tII) which is related to the high‐temperature tetragonal structure (tI). The transformation pressure exhibits hysteresis and is cycle dependent. At room temperature, the initial transformation pressure for the monoclinic‐tII transition on a virgin monoclinic crystal can be as high as 4.4 GPa; on subsequent cycling the transition pressure ultimately lowers to 3.29 ± 0.06 GPa. The pressure for the reverse transition is essentially constant at 2.75 ± 0.06 GPa. At pressures > 16.6 GPa, the tII form transforms to the orthorhombic cotunnite (PbCl2) structure. With increasing temperature, the tII form transforms to the high‐temperature tetragonal phase. For increasing P and T, the monoclinic‐tI‐tII triple point is located at T= 596°± 18°C and P= 2.26 ± 0.28 GPa, whereas for decreasing P and T, the triple point is found at T= 535°± 25°C and P= 1.7 ± 0.28 GPa.

Generation of static pressures above 2.5 megabars in a diamond-anvil pressure cell

A static pressure of 2.75 Mbars has been generated in a diamond-anvil pressure cell. This pressure is 1 Mbar higher than the highest static pressure previously produced in a laboratory, 1.72 Mbar by Mao and Bell [Science 200, 1145 (1978)]. Improvements in the geometry of the cut of beveled anvil surfaces, selection of diamond anvils for a high concentration of nitrogen platelets, and modifications in the design of the supporting cell for the diamond anvils resulted in the attainment of 2.75 Mbars. Pressures from 1 bar to 1.85 Mbar were measured by the ruby fluorescence method. The ruby fluorescence, however, was found to diminish in intensity with increasing pressure and to become undetectable at 1.85 Mbar. Pressures above 1.85 Mbar were calculated on the assumption of elastic behavior for the diamond anvils in two ways: (1) by extrapolation of the relationship between central pressure and force applied to the anvils, and (2) by extrapolation of radial pressure profiles. Three lines of evidence confirm that the diamond anvils behaved elastically, rather than deforming plastically, to the highest pressure achieved. The design improvements reported in this paper should result in the acquisition of a wide range of data in diamond cells at pressures above 1 Mbar, pressures at which virtually no static data have been obtained. Pressures substantially above 2.75 Mbars are probably attainable with the present design of the diamond-cell apparatus.

The crystal structure of forsterite Mg2SiO4 under high pressure up to 149 kb

Abstract Using a miniature diamond-anvil pressure cell and by means of single-crystal four-circle diffractometry, the crystal structure of synthetic forsterite has been studied up to 149 kb. The results are: (1) the distortion of the oxygen lattice from that of an ideal hexagonal closest packing (hcp) decreases with an increase of pressure, the extrapolation of the variation mode showing that the oxygen lattice would be ideally of the hcp type at around 160 kb. (2) While the mean Mg(2) – O bond shows a linear decrease with an increase of pressure, the mean Mg(1) – O distance ceases decreasing at around 80 kb. The value at this pressure is kept constant up to the experimental limit of 149 kb. At this extreme pressure both mean values are 2.05 Å. (3) The bulk modulus for the mean Si – O bond shows a value of 1.9 Mb.