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The so-called “Missing Xe” problem is a long standing unsolved problem and is related to many fields in Earth science: formation process and evolution of the Earth, origin and evolution of the atmosphere, and geochemistry. Although the long-held expectation was the retention of xenon in the iron-rich core, present experimental result clarified that it is unlikely to occur. This implies that we have to reconsider the missing xenon problem and encourage many scientists to pursuit other possibilities.

The phase relations and compression behavior of MnTiO3 perovskite were examined using a laser-heated diamond-anvil cell, X-ray diffraction, and analytical transmission electron microscopy. The results show that MnTiO3 perovskite becomes unstable and decomposes into MnO and orthorhombic MnTi2O5 phases at above 38 GPa and high temperature. This is the first example of ABO3 perovskite decomposing into AO + AB2O5 phases at high pressure. The compression behavior of volume, axes, and the tilting angle of TiO6 octahedron of MnTiO3 perovskite are consistent with those of other A2+B4+O3 perovskites, although no such decomposition was observed in other perovskites. FeTiO3 is also known to decompose into two phases, instead of transforming into the CaIrO3-type post-perovskite phase and we argue that one of the reasons for the peculiar behavior of titanate is the weak covalency of the Ti–O chemical bonds.

Raman studies of a high-pressure structure of hydrogen hydrate, a filled ice Ic structure, were performed using a diamond anvil cell in the pressure range 3.2–44.1 GPa. The Raman spectra of a vibron revealed that extraction of hydrogen molecules from the filled ice Ic structure occurred above 20 GPa. In addition, the Raman spectra of a roton revealed that a rotation of hydrogen molecules in the filled ice Ic structure was suppressed at around 20 GPa and then the rotation recovered, and the rotation of hydrogen molecules was suppressed again above 35.5 GPa. These results indicate that intermolecular interactions increased between guest hydrogen molecules and host water molecules at around 20 and 35.5 GPa. These intermolecular interactions were considered to be induced to stabilize the filled ice Ic structure. Above 40 GPa, symmetrization of hydrogen bond was considered to contribute to the stability of hydrogen hydrate.

A series of π-conjugated alternating copolymers consisting of Th-ITN-Th and p-C 6 H 2 (OR) 2 units were synthesized. XRD indicated that the copolymers assume an interdigitation packing mode, and UV-Vis spectra revealed a strong tendency for self-assembly. Upon molecular assembly of the copolymer, the UV-Vis absorption shifted by about 100 nm to a longer wavelength from that of the single molecule. The copolymers underwent electrochemical oxidation (or p-doping) and reduction (or n-doping) at 0.2 and -2.0 V versus Ag + /Ag, respectively. A p-doped copolymer film showed an electrical conductivity of 182 S · cm -1 , and the temperature dependence of electrical conductivity was measured. The copolymer showed piezochromism and served as a p-channel material for a field-effect transistor.

Compression behaviors of CaIrO3 with perovskite (Pv) and post-perovskite (pPv) structures have been investigated up to 31.0(1.0) and 35.3(1) GPa at room temperature, respectively, in a diamond-anvil cell with hydrostatic pressure media. CaIrO3 Pv and pPv phases were compressed with the axial compressibility of β a > β c > β b and β b > β a > β c, respectively and no phase transition was observed in both phases up to the highest pressure in the present study. The order of axial compressibility for pPv phase is consistent with the crystallographic consideration for layer structured materials and previous experimental results. On the other hand, Pv phase shows anomalous compression behavior in b axis, which exhibit constant or slightly expanded above 13 GPa, although the applied pressure remained hydrostatic. Volume difference between Pv and pPv phases was gradually decreased with increasing pressure and this is consistent with the results of theoretical study based on the ab initio calculation. Present results, combined with theoretical study, suggest that these complicate compression behaviors in CaIrO3 under high pressure might be caused by the partially filled electron of Ir4+. Special attention must be paid in case of using CaIrO3 as analog materials to MgSiO3, although CaIrO3 exhibits interesting physical properties under high pressure.

Lattice-preferred orientations (LPOs) of post-perovskite (PPv)-type MgGeO 3 formed by transformations from two different pre-phases, orthopyroxene (OPx) and perovskite (Pv), were studied using radial and axial X-ray diffraction techniques combined with a laser-heated diamond-anvil cell. When the PPv was made from Pv, strong LPO was formed in the PPv immediately after the transformation with an alignment of the (0 0 1) or (0 1 1) plane almost perpendicular to the compression axis. This present result contrasts markedly from that observed when the PPv was formed from OPx and those reported on MgGeO 3 -PPv and (Mg,Fe)SiO 3 -PPv transformed from OPx, in which the (1 0 0) or (1 1 0) plane was aligned to the compression axis. It was clarified that when the PPv-type MgGeO 3 is formed in diamond-anvil cells, it has strong transformation-induced LPO from the beginning even before plastic deformation occurs, and that its characteristics depend on the pre-phase before the transformation. The formed transformation-induced LPO of PPv did not change in spite of further compression using a conventional gasket because the sample became too thin to deform. However, by using a diamond gasket technique, we were able to deform the PPv at room temperature, resulting in significant variations of the relative intensities of several diffraction peaks. The change in the axial diffraction patterns can be explained only by assuming that the (0 0 1) plane aligns almost perpendicularly to the compression axis. The present results suggest that the (0 0 1) is a dominant slip plane in MgGeO 3 -PPv at room temperature. If one makes the assumption that the dominant slip system(s) of silicate PPv deformed in the D″ layer is or are identical to that of germanate PPv at room temperature, then a large S-wave polarization anisotropy in the Earth's D″ layer would be explained by the small degree of deformation-induced LPO of the PPv phase that is expected to exist in this layer.

Single crystals of rutile-type GeO 2 having a structure equivalent to that of TiO 2 , a well-known photocatalyst, have been grown for the first time in supercritical oxygen at approximately 5 GPa and 3000 K. The obtained crystals exhibit a rectangular hollow tube structure with submicron size (cross section with sides of ∼500 nm, wall thickness of ∼20 nm, and longitudinal length of ∼5 μm). These single crystals were grown within 1 s and along the c -axis surrounded by the (1 1 0) faces. The crystal growth mechanism strongly depends on the growth mechanism of rutile-type oxides, and the extremely short growing time is an important factor in the formation of hollow tube crystals.

Laser heating in diamond anvil cell (DAC) equipped with nano-polycrystalline diamond (NPD) anvils was tested for the first time using various types of lasers. An NPD-based DAC was found to provide better heating efficiency than a standard DAC with single-crystal anvils, probably due to the order of magnitude lower thermal conductivity of the NPD. We observed high-temperature generation exceeding 5000 and 3500 K during laser heating of hcp-Fe sample at pressures of ∼100 and ∼170 GPa, respectively. The results of the present study demonstrate promising potential of laser-heated nano-polycrystalline DAC for the generation of very high temperature under multi-megabar pressure conditions equivalent to those of the Earth's core.

This paper reports a procedure to combine the focused ion beam micro-sampling method with conventional Ar-milling to prepare high-quality site-specific transmission electron microscopy cross-section samples. The advantage is to enable chemical and structural evaluations of oxygen dissolved in a molten iron sample to be made after quenching and recovery from high-pressure experiments in a laser-heated diamond anvil cell. The evaluations were performed by using electron energy-loss spectroscopy and high-resolution transmission electron microscopy. The high signal to noise ratios of electron energy-loss spectroscopy core-loss spectra from the transmission electron microscopy thin foil, re-thinned down to 40 nm in thickness by conventional Argon ion milling, provided us with oxygen quantitative analyses of the quenched molten iron phase. In addition, we could obtain lattice-fringe images using high-resolution transmission electron microscopy. The electron energy-loss spectroscopy analysis of oxygen in Fe(0.94)O has been carried out with a relative accuracy of 2%, using an analytical procedure proposed for foils thinner than 80 nm. Oxygen K-edge energy-loss near-edge structure also allows us to identify the specific phase that results from quenching and its electronic structure by the technique of fingerprinting of the spectrum with reference spectra in the Fe-O system.

The post-corundum phase transition has been investigated in Ti2O3 on the basis of synchrotron X-ray diffraction in a diamond anvil cell and transmission electron microscopy. The new polymorph of Ti2O3 was found at about 19 GPa and 1850 K, and this phase was stable even at about 40 GPa. A new polymorph of Ti2O3 can be indexed on a Pnma orthorhombic cell, and the unit-cell parameters are a=7.6965 (19) A, b=2.8009 (9) A, c=7.9300 (23) A, V=170.95 (15) A3 at 19 GPa, and a=7.8240 (2) A, b=2.8502 (1) A, c=8.1209 (3) A, V=181.10 (1) A3 at ambient conditions. The Birch–Murnaghan equation of state yields K 0=206 (3) GPa and K′0=4 (fixed) for corundum phase, and K 0=296 (4) GPa and K′0=4 (fixed) for the post-corundum phase. The molar volume decreases by 12% across the phase transition at around 20 GPa. The structural identification was carried out on a recovered sample by the Rietveld method, and a new polymorph of Ti2O3 can be identified as Th2S3-type rather than U2S3-type structure. The transition from corundum-t...

The compression behaviors of δ-AlOOH and δ-AlOOD were investigated under quasi-hydrostatic conditions at pressures up to 63.5 and 34.9 GPa, respectively, using results from synchrotron X-ray diffraction experiments conducted at ambient temperature. Because of the geometric isotope effect, at ambient pressure, the a and b axes of δ-AlOOD, which define the plane in which the hydrogen bond lies, are longer than those of δ-AOOH. Under increasing pressure, the a and b axes of δ-AlOOH stiffen at 10 GPa, although the c axis shows no marked change. Identical behavior was found in δ-AlOOD, but the change in compressibility was observed at a slightly higher pressure of 12 GPa. Axial ratios a / c and b / c first decrease rapidly with increasing pressure, then begin to increase at pressures >10 GPa in δ-AlOOH and >12 GPa in δ-AlOOD. At these pressures, the pressure dependence of a / b also changes from increasing to decreasing. The unit-cell volumes of δ-AlOOH and δ-AlOOD become slightly less compressible at high pressures. Assuming K ′ = 4, the calculated bulk moduli of δ-AlOOH below and above 10 GPa are 152(2) and 219(3) GPa, respectively. Those of δ-AlOOD below and above 12 GPa are 151(1) and 207(2) GPa, respectively.

Self-assembly of polythiophenes with –C≡CR (R = alkyl, phenyl, etc.) side chains has been investigated. Seven new polymers consisting of head-to-head and tail-to-tail 2,2′-bithiophenes with –C≡CR s...

The stability and equation of state for the cotunnite phase in TiO2 were investigated up to a pressure of about 70 GPa by high-pressure in situ X-ray diffraction measurements using a laser-heated diamond anvil cell. The transition sequence under high pressure was rutile → α-PbO2 phase → baddeleyite phase → OI phase → cotunnite phase with increasing pressure. The cotunnite phase was the most stable phase at pressures from 40 GPa to at least 70 GPa. The equation of state parameters for the cotunnite phase were established on the platinum scale using the volume data at pressures of 37–68 GPa after laser annealing, in which the St value, an indicator of the magnitude of the uniaxial stress component in the samples, indicates that these measurements were performed under quasi-hydrostatic conditions. The third-order Birch-Murnaghan equation of state at K 0′ = 4.25 yields V 0 = 15.14(5) cm3/mol and K 0 = 294(9), and the second-order Birch-Murnaghan equation of state yields V 0 = 15.11(5) cm3/mol and K 0 = 306(9). Therefore, we conclude that the bulk modulus for the cotunnite phase is not comparable to that of diamond.

Equations of state and axial compressions are investigated for the Mg0.9Fe0.1SiO3 and Mg0.85Fe0.15Al0.15Si0.85O3 postperovskite phases in the MgSiO3–FeSiO3–FeAlO3 system by high-pressure in situ X-ray diffraction measurements using a laser-heated diamond anvil cell. The b-axis is found to be the most compressible axis for both phases, while the c-axis is slightly less compressible. The incompressible behavior of the c-axis is likely to be attributable to repulsion among oxygen atoms arranged along the c-axis. Using the Tsuchiya gold pressure scale, the Birch–Murnaghan equation of state yields isothermal bulk moduli of 224(11) GPa and 220(13) GPa, and zero-pressure unit-cell volumes of 164.1(15) A3 and 166.5(20) A3 for these FeSiO3- and FeAlO3-bearing postperovskites, respectively. The incorporation of FeSiO3 and FeAlO3 into the MgSiO3 postperovskite results in a marked decrease in the isothermal bulk modulus. The bulk sound velocity is also confirmed to decrease considerably at the perovskite–postperovskite transition, even in the FeSiO3- and FeAlO3-bearing systems. The velocity thus decreases not only by the postperovskite transition but also by enrichment in the FeSiO3 and FeAlO3 components. Chemical heterogeneity of the FeSiO3 and FeAlO3 components may therefore represent an additional mechanism of velocity variation in the D″ layer of the lower mantle.

In situ X-ray diffraction measurements of CaFe 2 O 4 -type MgAl 2 O 4 have been conducted at pressures up to 42 GPa and temperatures to 2400 K using Kawai-type multianvil apparatus with sintered diamond anvils. Additional measurements have also been conducted at pressures to 12 GPa using diamond anvil cell with helium as a pressure medium at room temperature, and at temperatures to 836 K at the ambient pressure using a high-temperature X-ray diffractometer. The analysis of room-temperature data yielded V 0 = 240.1(2) A 3 , K 0 = 205(6) GPa, and K ′ 0 = 4.1 ( 3 ) . A fit of the present data to high-temperature Birch–Murnaghan equation of state (EOS) yielded (∂ K 0 /∂ T ) P = −0.030(2) GPa/K and α 0 = a 0 + b 0 T with values of a 0 = 1.96(13) × 10 −5 K −1 and b 0 = 1.64(24) × 10 −8 K −2 . The present data set was also fitted to Mie–Gruneisen–Debye (MGD) EOS and we obtained γ 0 = 1.73(7), q = 2.03(37), and θ 0 = 1546(104) K. Density changes of MORB have been estimated using the newly obtained thermoelastic parameters, assuming that the Al-rich phase in this composition possesses the CaFe 2 O 4 -type structure under the lower mantle P , T conditions. The calculated densities along geotherms for the normal mantle and subducting cold slabs are both significantly higher than those of typical seismological models, confirming the conclusion of some recent results on MORB by laser-heated diamond anvil cell experiments.

Dislocation microstructures of polycrystalline MgSiO3 perovskite, synthesized in a multi-anvil type high-pressure apparatus at 26 GPa and 2023 K for 600 min, have been investigated using transmission electron microscopy (TEM). The recovered MgSiO3 perovskite displayed deformation lamellae under cross-polarized optical microscopy, suggesting that the sample was deformed during the high-pressure experiment. TEM observations showed that curved dislocations with Burgers vectors lying in the {1 1 0} plane, potentially b = 〈1 1 0〉 and [ 0 0 w ] (orthorhombic symmetry) were nucleated. Low-angle tilt boundaries controlled by 〈1 1 0〉 dislocation climb were also activated at high temperature and pressure. The potential Burgers vector of b = 〈1 1 0〉 is consistent with previous results of slip to 〈1 0 0〉cubic, [1 0 0]pc and [0 1 0]pc (cubic symmetry and pseudo-cubic symmetry) on non-silicate perovskite analogues deformed at high temperatures and ambient pressure. The microstructures of climb-accommodated dislocation creep controlled by diffusion in the MgSiO3 perovskite can provide useful information on the rheology at high temperatures and slow strain rates corresponding to the Earth's lower mantle.

We have synthesized Ln nitrides (Ln = Ce, Pr, Gd, Lu) in a supercritical nitrogen fluid at high pressure (about 30 GPa) and high temperature (about 2000 K) using the diamond anvil cell and YAG laser heating system. New Ce and Pr nitrides have been synthesized, while the well-known NaCl-type GdN and LuN have been obtained. It is found that the structures of the new Ce and Pr nitrides are different from those of the new La nitrides reported recently.

Radial X-ray diffraction measurements are performed on CaSiO3perovskite between 25.5 and 49.3 GPa at 300 K. The Rietveld method is used to extract quantitative texture and stress information. We find some mismatches in lattice strains evaluated in the Rietveld method with variations of d-spacings for 2 0 0 and 2 1 0 over-estimated while those for 1 1 1 are under-estimated and attribute it to the effect of plastic deformation. The differential stress supported by CaSiO3 perovskite in this study is approximately twice as large as previous measurements and the ratio of differential stress to shear modulus t / G varies between 5.4% and 7.2% between 25 and 49 GPa. The sample displays preferred orientation of the {1 0 0} planes perpendicular to the compression direction, compatible with slip on { 1 1 0 } 〈 1 1 ¯ 0 〉 .

Spin transition has attracted the interest of researchers in various fields since the early 1930s, with thousands of examples now recognized, including those in minerals and biomolecules. However, so far the metal centres in which it has been found to occur are almost always octahedral six-coordinate 3d4 to 3d7 metals, such as Fe(II). A five-coordinate centre is only rarely seen. Here we report that under pressure SrFe(II)O2, which features a four-fold square-planar coordination, exhibits a transition from high spin (S = 2) to intermediate spin (S = 1). This is accompanied by a transition from an antiferromagnetic insulating state to a ferromagnetic so-called half-metallic state: only half of the spin-down (dxz, dyz) states are filled. These results highlight the square-planar coordinated iron oxides as a new class of magnetic and electric materials., 四本の手をもつ金属原子の磁性の変換に成功 －磁気記録、スイッチ素子の革新につながるか－. 京都大学プレスリリース. 2009-07-21.

Nanograin size of about 3-5nm of 20mol% Y-doped BaZrO3 (BZY20) proton conducting solid electrolyte has been prepared at low processing temperature (

High pressure studies of solid methane were performed using diamond anvil cells in the pressure range of 0.5–86 GPa. X-ray diffractometry and Raman spectroscopy revealed two high pressure phases above 35 GPa. The results suggested that the observed high pressure phases have a fundamental structure similar to that of a reported high pressure phase, but they exhibit the orientational ordering of molecules in a different manner. An intermediate metastable phase was found between known phase A and phase B, which showed a structure close to that of phase B but showed rotation of molecules close to that of phase A.

Head-to-head type poly(3-(1-dodecynyl)thiophene-2,5-diyl), HH-P3(C CDec)Th, formed a well aligned structure in its cast film, and UV–vis absorption peak of the cast film showed a large shift by about 110 nm to a longer wavelength from that (518 nm) observed in solution. Under high pressure HH-P3(C CDec)Th exhibited clear piezochromism; the UV–vis absorption peak at about 605 nm observed under atmospheric pressure shifted to 672 nm under 10.71 GPa, suggesting an increase in electronic interaction between the polymer molecules under high pressure. The π–π ∗ transition energy decreased by 0.028 eV/GPa in the range of 0–5.2 GPa.

We performed high-pressure and high-temperature X-ray diffraction experiments on InOOH using laser heated diamond anvil cells. After heating at 1300 K, pyrite-type InOOH was formed at 14 GPa and it was stable up to at least 30 GPa. Pyrite-type InOOH partially transformed back to distorted rutile-type InOOH after recovery. The lattice constant and unit-cell volume of pyrite-type InOOH were determined to be a0 = 5.3151(8) A and V0 = 150.15 (7) A3 at ambient conditions, respectively. The density difference between pyrite-type and distorted rutile-type InOOH was 5% at ambient condition.

Lattice preferred orientations (LPO) developed in perovskite and post-perovskite structured CaIrO3 were studied using the radial X-ray diffraction technique combined with a diamond anvil cell. Starting materials of each phase were deformed from 0.1 MPa to 6 GPa at room temperature. Only weak LPO was formed in the perovskite phase, whereas strong LPO was formed in the post-perovskite phase with an alignment of the (010) plane perpendicular to the compression axis. The present result suggests that the (010) is a dominant slip plane in the post-perovskite phase and it is in good agreement with the crystallographic prediction, dislocation observations via transmission electron microscopy, and a recent result of simple shear deformation experiment at 1 GPa–1,173 K. However, the present result contrasts markedly from the results on MgGeO3 and (Mg,Fe)SiO3, which suggested that the (100) or (110) is a dominant slip plane with respect to the post-perovskite structure. Therefore it is difficult to discuss the behavior of the post-perovskite phase in the Earth’s deep interior based on existing data of MgGeO3, (Mg,Fe)SiO3 and CaIrO3. The possible sources of the differences between MgGeO3, (Mg,Fe)SiO3 and CaIrO3 are discussed.

We have succeeded in synthesizing two new lanthanum nitrides in a supercritical nitrogen fluid at high pressure (about 30 GPa) and high temperature (about 2000 K), using a diamond anvil cell and a YAG laser heating system. These nitrides were found to be stable down to 5 GPa and ∼300 K in a nitrogen atmosphere. One of the new lanthanum nitrides is a cubic P lattice-type phase, which is a main phase synthesized nitride. The calculated lattice parameter is a = 11.979 A at 5 GPa, 300 K. The other nitride is of a trigonal P lattice-type. The calculated lattice parameters are a = 3.889 A and c = 6.691 A at 5 GPa, 300 K. The most likely phase of the former new La nitride is Pa 3 La 2 N 3 + δ , the structure of which may be similar to the Ia 3 Mn 2 O 3 -type (Ia80). The phase of the latter nitride is P 3 m 1 La 2 N 3 + δ , the structure of which is the same as the P 3 m 1 La 2 O 3 -type (hP5).

In situ X-ray diffraction measurements of Fe- and Al-bearing MgSiO3-rich perovskite (FeAl-Pv), which was synthesized from a natural orthopyroxene, were performed at pressures of 19–32 GPa and temperatures of 300–1,500 K using a combination of a Kawai-type apparatus with eight sintered-diamond anvils and synchrotron radiation. Two runs were performed using a high-pressure cell with two sample chambers, and both MgSiO3 perovskite (Mg-Pv) and FeAl-Pv were synthesized simultaneously in the same cell. Thus we were able to measure specific volumes (V/V0) of Mg-Pv and FeAl-Pv at the same P−T conditions. At all the measurement conditions, values of the specific volume of FeAl-Pv are consistent with those of Mg-Pv within 2 Standard Deviation, strongly suggesting that effect of incorporation of iron and aluminum on the thermoelastic properties of magnesium silicate perovskite is undetectable in this composition, pressure, and temperature range. Two additional runs were performed using a high-pressure cell that has one sample chamber and unit-cell volumes of FeAl-Pv were measured at pressures and temperatures up to 32 GPa and 1,500 K, respectively. All the unit-cell volume data of FeAl-Pv perovskite were fitted to the high temperature Birch–Murnaghan equation of state and a complete set of thermoelastic parameters of this perovskite was determined with an assumption of K′300,0 = 4. The determined parameters are K300,0 = 243(3) GPa, (∂KT,0/∂T)P = −0.030(8) GPa/K, a0 = 2.78(18) × 10−5 K−1, and b0 = 0.88(28) × 10−8 K−2, where a0 and b0 are the coefficients of the following expression describing the zero-pressure thermal expansion: αT,0 = a0 + b0T. The equation-of-state parameters of FeAl-Pv are in good agreement with those of MgSiO3 perovskite at the conditions corresponding to the uppermost part of the lower mantle.

High-pressure Raman studies of methane hydrate were performed using a diamond anvil cell in the pressure range of 0.1–86 GPa at room temperature. Raman spectra of the methane molecules revealed that new softened intramolecular vibration mode of ν 1 appeared at 17 GPa and that the splitting of vibration mode of ν 3 occurred at 15 GPa. The appearance of these two modes indicates that an intermolecular attractive interaction increases between the methane molecules and the host water molecules and between the neighboring methane molecules. These interactions might result in the exceptional stability of a high-pressure structure, a filled ice Ih structure (FIIhS) for methane hydrate, up to 40 GPa. At 40 GPa, a clear change in the slope of the Raman shift versus pressure occurred, and above 40 GPa the Raman shift of the vibration modes increased monotonously up to 86 GPa. A previous XRD study showed that the FIIhS transformed into another new high-pressure structure at 40 GPa. The change in the Raman spectra at 40 GPa may be induced by the transition of the structure.

The new filled skutterudite TbFe4P12 has been prepared at around 4 GPa and 1050 °C. Powder X-ray diffraction of TbT4P12 (T = Fe and Ru) has been studied with synchrotron radiation at ambient pressure. The crystal structures of both compounds were refined by Rietveld methods at ambient pressure. The positional parameters, bond lengths and bond angles have been obtained for TbT4P12 (T = Fe and Ru). The electrical and magnetic properties of TbFe4P12 have been investigated at low temperatures. The susceptibility of this phosphide follows a Curie-Weiss behavior at higher temperatures. The linear slope of the χ−1 vs. T curve from 15 to 300 K yields an effective magnetic moment of 9.48 μB. This value is close to the magnetic moment of the Tb3+ ion calculated from Hund’s rule, 9.72 μB. The ferromagnetic transition of TbFe4P12 was observed at around 10 K, and an electrical anomaly based on the magnetic ordering was detected. The relationship between the crystal structure and the physical properties of TbT4P12 (T = Fe and Ru) is discussed.

High-pressure experiments regarding two filled-ice hydrogen hydrates, C1 and C2, were performed in a pressure range of 0.2−8.0 GPa at room temperature using a diamond anvil cell. According to the first repot of these hydrates by other workers, the hydrogen molecules in C1 are located interstitially in an ice II lattice and those in C2 are in an ice Ic lattice. Changes in the Raman frequencies of these hydrates' hydrogen vibrons with pressure were revealed by Raman spectroscopy combined with X-ray diffractometry. Hydrogen molecules in C1 showed vibration frequencies slightly higher than or similar to those in the fluid at the same pressures, while those in C2 showed frequencies approximately 20 cm-1 higher than those in C1. The OH-stretching mode of the water molecules of C1 was higher than that of the host ice structures of ice II, while that of C2 was lower than that of ice VII. This difference in OH-stretching modes between C1 and C2 was explained in relation to the intermolecular distances of the water...

The present paper readdresses the issue of stress and strain analysis for hcp-metals plastically deformed under high pressure in the diamond anvil cell with an application to cobalt at 42 GPa. The effective single crystal elastic moduli deduced from radial X-ray diffraction under Reuss or geometric averages, including effects of lattice preferred orientations, and assuming a constant stress within the sample, consistently differ from those measured with other technique with the largest deviations observed on C 44 . These results are then interpreted as an (hkl)-dependent effective differential stress.

The Rietveld method is used to extract quantitative texture information from a single synchrotron diffraction image of a CaSiO(3) perovskite sample deformed in axial compression in a diamond anvil cell. The image used for analysis was taken in radial geometry at 49 GPa and room temperature. We obtain a preferred orientation of {100} lattice planes oriented perpendicular to the compression direction and this is compatible with [Formula: see text] slip.

High-pressure experiments of methane hydrate with a composition of full-occupancy of structure I were performed in a pressure range from 0.2 to 86 GPa. X-ray diffractometry and Raman spectroscopy revealed that methane hydrate transformed from a known high-pressure structure, filled-ice-Ih structure, to a new high-pressure structure at approximately 40 GPa. The reason for the outstanding retention of the filled-ice-Ih structure up to 40 GPa was examined, because the filled-ice-Ih structures for other gas hydrates decompose below 6.5 GPa. In the Raman spectra, new intramolecular vibration modes softer than the original ones appeared at 14 to 17 GPa, indicating that additional intermolecular interaction arose around the methane molecules. The additional interaction might be induced by symmetrization of the hydrogen bonds forming the framework. The symmetrization of the framework and the subsequent additional interactions between the methane molecules and the framework water molecules and also between the methane molecules are likely the cause of the excellent stabilization. The new high-pressure structure survived at least to 86 GPa.

High-pressure and high-temperature experiments on methane hydrate were performed using a diamond anvil cell under conditions of 0.2–86 GPa and at room temperature to 1000 K. In situ X-ray diffraction studies revealed that a known high-pressure structure, filled ice Ih structure, of methane hydrate transformed to a new high-pressure structure at 40 GPa, and this structure was maintained to 86 GPa. No decomposition into solid methane and ice VII was observed until 86 GPa. In the heating treatments at 50 and 86 GPa, the new high-pressure structure of methane hydrate survived up to 1000 K without decomposition.

A new skutterudite compound LaxRh4P12 has been prepared at around 1100 °C and 4 GPa. This product was characterized by powder x-ray diffraction at ambient pressure. The x-ray diffraction profile of LaxRh4P12 is indexed to the filled skutterudite-type structure. The lattice constant of this sample is 8.0581(5) A. The x value estimated from x-ray diffraction and electron probe microanalysis data is about 0.6. Electrical and magnetic properties of this compound have been studied at low temperatures. LaxRh4P12 showed a superconducting transition at around 17 K. This compound has the highest Tc among metal phosphides. The thermoelectric power of the new compound is negative, S = −47 µV K−1, at room temperature. The new superconducting material LaxRh4P12 is an n-type conductor.

Syntheses of 3d-transition metal (Ti–Cu) nitrides have been tried in a supercritical nitrogen fluid at high pressures (about 10 GPa) and high temperatures (about 1800 K) using diamond anvil cell and YAG laser heating system. Nitrides, such as TiN, VN, CrN, Mn3N2, Fe2N, Co2N and Ni3N have been successfully synthesized easily by a simple direct nitriding reaction between metal and fluid nitrogen in a short time, while any Cu nitrides were not synthesized. These results indicate that the ratio of nitrogen to metal, N/M, of the nitride decreases from 1 to 0 with the sequence from the early transition metal nitrides to the late transition metal ones. The systematic change of the N/M ratio and crystal structure of the 3d-transition metal nitrides is discussed and interpreted on the basis of the electron arrangement of the 3d-transition metal which is relevant to its coordination number.

Synthesis of cobalt nitrides has been tried in a supercritical nitrogen fluid at high pressure (about 10 GPa) and high temperature (about 1800 K) using diamond anvil cell and YAG laser heating system. We have succeeded to synthesize a single phase of the CFe2-type Co2N easily in a short time. This is the first synthesis by a simple reaction between the pure cobalt and pure nitrogen (supercritical fluid nitrogen). The cell parameters of the synthesized Co2N are a=4.662(9) A, b=4.332(5) A and c=2.749(9) A, respectively.

New filled skutterudites LnFe4P12 (Ln = Ho, Er, Tm and Yb) and YRu4P12 with heavy lanthanide (including Y) have been prepared at high temperatures and high pressures. Electrical and magnetic properties of these compounds have been studied at low temperatures. The magnetic susceptibility of HoFe4P12 and ErFe4P12 follows the Curie–Weiss behaviour at higher temperatures. The linear slope of χ−1 versus T curves yields effective magnetic moments of 10.43 μB for HoFe4P12 and 9.59 μB for ErFe4P12. These values are in good agreement with magnetic moments of Ho3+ and Er3+ ions calculated from Hund's rule, 10.60 and 9.69 μB, respectively. HoFe4P12 shows a ferromagnetic transition at around 5 K. TmFe4P12 and YbFe4P12 exhibit the paramagnetic behaviour at low temperatures. The lattice constant of YbFe4P12 is 7.7877(5) A, larger than the value expected from the skutterudite compounds with the oxidation state of +3. This compound may be in an intermediate valence state. YRu4P12 shows the superconducting transition at around 8.5 K. This compound is a new superconductor. The Tc of YRu4P12 is higher than that of YFe4P12 and YOs4P12, and is highest among the metal phosphides with a skutterudite-type structure.

We have carried out in-situ X-ray diffraction experiments on high-pressure transformations of a Ca- and Fe- rich pyroxene (Ca 1 . 0 3 Mg 0 . 6 1 Fe 0 . 2 3 Al 0 . 1 4 Si 2 O 6 ) to investigate the stability of Ca 0 . 5 (Mg, Fe, Al) 0 . 5 SiO 3 perovskite (CM-perovskite) in a multi component system at about 32 GPa and up to 1900 °C. We observed that cubic CM-perovskite was formed at about 1300 °C and decomposed into cubic Ca-perovskites and orthorhombic Mg-perovskites and stishovite at 1800 °C when using a glass starting material. In another experiment using a crystalline pyroxene starting material, two cubic perovskites; Ca-perovskite and CM-perovskite, and orthorhombic Mg-perovskite formed simultaneously during the initial stage of the transformation. However, the cubic CM-perovskite subsequently decomposed into Mg- and Ca-perovskites and stishovite at 1200 °C. These results indicate that the assembly of cubic Ca-perovskite, orthorhombic Mg-perovskite and stishovite is stable and cubic CM-perovskite is a metastable phase at around 32 GPa and temperatures over 1000 °C in this system. Chemical analyses of product phases showed that Mg, Fe, and Al were preferentially partitioned into Mg-perovskite and the compositions of Ca-perovskite were close to pure CaSiO 3 . The present study shows that CM-perovskite nucleates during the initial stage of Ca(Mg, Fe, Al)Si 2 O 6 pyroxene transformation. Therefore, cold subducting slabs and impacted meteorites are the possible places in which CM-perovskite could exist. The Ca-rich glassy phase in a shocked chondrite (Tomioka and Kimura 2003) might have formed by vitrification of a metastable CM-perovskite-like phase.

We have investigated the elastic properties of the Sm-based filled skutterudite compound SmOs4P12 for the first time. The measurements were performed on polycrystalline samples prepared at high temperatures and high pressures by using a wedge-type, cubic anvil, high-pressure apparatus. A clear and steep decrease was observed at an antiferromagnetic transition temperature of 4.5 K in the temperature dependence of both the longitudinal and the transverse elastic constants. Absence of a precursor behavior reminds us of the multipolar ordering, possibly octupolar ordering, observed in the isostructural system SmRu4P12. The transition is robust against an external magnetic field. We argue that the low-lying degenerate levels derived from the 4f-multiplet ground state of the Sm ion is split by the crystalline electric field in SmOs4P12. Furthermore, we discuss the phononic properties, which include the ionic degrees of freedom for the rattling motion, and compare them with the values for other isostructural systems.

The stability of cubic bismuth orthogermanate Bi4(GeO4)3 is investigated at high pressure (HP) and high temperature (HT) using x-ray diffraction, Raman spectroscopy, and scanning electron microscopy (SEM). At ambient temperature the compound is found to have a bulk modulus of 48 ± 2 GPa and it undergoes amorphization at 12.5 GPa, whereas in situ laser heating of amorphous sample in a diamond-anvil cell results in re-crystallization. SEM and Raman spectroscopy of the recovered sample suggest an inhomogeneous sample with regions rich and depleted in Ge, suggesting a decomposition of the parent compound. The decomposition products are identified from the x-ray diffraction. These results show that at HP–HT the compound exhibits complex decomposition paths leading to several mixed oxide phases including α-Bi2O3, Bi2GeO5, and Bi2Ge3O9. The observations of pressure-induced amorphization at ambient temperature in this compound and its decomposition into a mixture of daughter phases at HP–HT are discussed in light of a recent model of pressure-induced amorphization and decomposition.

Recent studies have contributed a great deal to our understanding of the structural changes in gas hydrates under pressure. A feature of structural changes in terms of pressure and guest size is summarised in the former part of this paper. The gas hydrate with the guest size from argon to methane finally take a common filled ice Ih structure, although they have different initial and intermediate structures. In the latter part, retention of the filled ice Ih structure of methane hydrate up to 42 GPa is described. In situ X-ray diffractometry and optical observation revealed the existence of the filled ice structure with the volume change of 40% and large anisotropic compressibility. The distances between oxygen atoms estimated from the unit cell parameters suggested that symmetrization of hydrogen bonds occurred in the structure.

Majoritic garnet and silicate perovskite assemblages synthesised from natural pyroxene in the multi-anvil press and diamond anvil cell were studied by energy dispersive X-ray spectroscopy (EDXS) and electron energy-loss spectroscopy (EELS) in a transmission electron microscope (TEM) to quantify the composition and oxidation state of iron. In these assemblages of the (Mg, Fe)SiO3–Al2O3 system, Fe3+ has a much stronger affinity to silicate perovskite than to majoritic garnet at the same pressure, temperature and oxygen fugacity. To determine the site occupancy of iron in majoritic garnet and silicate perovskite, we have also performed both spectroscopic techniques (EDXS and EELS) under channelling conditions. Electron channelling spectroscopy enables the octahedral sites of both phases to be distinguished from other cation sites by variations in the intensity ratios of the EDXS and EELS spectra acquired systematically at tilting conditions about the channelling-sensitive crystal plane and zone axis. In majorite almost all of ferric iron is partitioned into the octahedral site, whereas in silicate perovskite both ferrous and ferric iron substitute preferentially into the pseudo-dodecahedral site of the perovskite structure. The latter is charge balanced by aluminium in the octahedral site.

A combined method of a laser-heated diamond anvil cell (DAC) experiment and analytical electron microscopy to study the mineralogy of the lower mantle was explored. Particularly, the use of ultramicrotomy to make ultrathin foils for analytical transmission electron microscopy (ATEM) of the ultrahigh pressure materials was explored with the aim of obtaining the exact chemical compositions of those materials with submicron size. Ultrathin foils with a thickness down to about 30 nm were obtained for ultrahigh pressure materials synthesized by a laser-heated DAC, although some areas of the foils were lost. Reliable chemical compositions were obtained with these foils using the experimentally obtained k -factors. The preliminary results on the mutual solubilities between (Mg,Fe)SiO 3 and CaSiO 3 perovskites with this method indicate that the (Mg,Fe) solubility in CaSiO 3 perovskite increases dramatically (up to 0.34 cations per foumula unit at 78 GPa and 1900 °C) with increasing the bulk iron content and/or pressure, while the Ca solubility in coexisting (Mg,Fe)SiO 3 perovskite remains very limited (0.01–0.02 cations per formula unit) under the same conditions.

The effect of alumina content on the compressibility of MgSiO3 perovskite was studied using both diamond-anvil and multi-anvil techniques. Hydrostatic compressions were performed on MgSiO3 perovskites using helium as a pressure-transmitting medium up to 33 GPa. Dissolution of up to 10 mol% Al2O3 clearly makes perovskite more compressible, and this effect was apparent even when only 1% Al2O3 was dissolved. On the other hand, no meaningful effect was observed when the measurement was made using the multi-anvil apparatus. Various results reported so far have shown widely scattered values, and it is difficult to explain this range of results. It is likely that one or more unknown parameters exist that have not yet been accounted for during experimentation. Further careful studies are required to provide an answer this question, which is important to a clear understanding of the lower mantle.

An in situ X-ray diffraction study of magnesiowustite at high pressures and high temperatures was performed using a high temperature diamond anvil cell and synchrotron radiation. A rhombohedral distortion starts in (Mg 0.20 ,Fe 0.80 )O, (Mg 0.10 ,Fe 0.90 )O, (Mg 0.05 ,Fe 0.95 )O and FeO at the same pressure of 16 GPa. The rhombohedral phase was observed even after laser annealing at megabar pressures. At high temperatures above 1500 °C and megabar pressures, a B1 (rock salt) structured phase was observed to be stable in all samples. A B8 (NiAs) structured phase was not found in magnesiowustite and was only observed in the end member FeO. The diffraction pattern of the B8 phase was consistent with the calculated intensities for the inverse B8 structure. The results indicate that the stable phase of magnesiowustite would have a B1 structure under lowermost mantle conditions.

New filled skutteudites LnOs 4 P 12 (Ln: Eu, Gd, Tb, Dy, Ho and Y) have been prepared at high temperatures and at high pressures. X-ray diffraction of these compounds is studied at room temperature. The relationship between lattice constants and atomic numbers of lanthanide (including Y) is obtained for LnOs 4 P 12 (Ln: lanthanide). Electrical and magnetic properties of the new filled skutterudites with heavier lanthanide have been investigated at low temperatures. EuOs 4 P 12 and GdOs 4 P 12 show ferromagnetic transitions at around 15 and 22 K, respectively. The valence states of both compounds are +2 for the Eu compound and +3 for the Gd compound. DyOs 4 P 12 does not show the magnetic transition down to 2 K. However, a small electrical anomaly is found at around 10 K. YOs 4 P 12 exhibits a superconducting transition at around 3 K. This compound is a new superconductor. Electrical and magnetic anomalies of new filled skutterudites with heavier lanthanide LnOs 4 P 12 (Ln: Eu, Gd, Dy and Y) are discussed. We have also found the electrical anomaly based on the magnetic transition at around 22 K for GdFe 4 P 12 .

Synthesis of metal nitrides has been tried in a supercritical nitrogen fluid at high pressures (about 10 GPa) and high temperatures yield using diamond anvil cell and YAG laser heating system. Transition-metal nitrides such as TiN, VN, Fe2N, ZrN, NbN, MoN and HfN can be easily synthesized by a direct nitriding reaction between metal and fluid nitrogen. Superconducting transition of TiN, VN, ZrN and NbN can be observed using one synthesized sample by a SQUID magnetometer. Colorless transparent fine crystals of GaN in the wultz-rock type structure can be also grown from gallium and fluid nitrogen. They have hexagonal platelet or prismatic morphology, indicating a solution growth using supercritical nitrogen fluid as a solvent. These results in this study open us a new way of synthesis and crystal growth of various kinds of nitrides in a supercritical nitrogen fluid under high temperatures and high pressures yield using diamond anvil cell and YAG laser heating.