| 1. |
|
|
| 2. |
- Tutti, F., et al.
(author)
-
Stability of KAlSi3O8 hollandite-type structure in the earth's lower mantle conditions
- 2001
-
In: Geophysical Research Letters. - 0094-8276. ; 28:14, s. 2735-2738
-
Journal article (peer-reviewed)abstract
- The stability of KAISi3O8 hollandite-type structure is investigated in a series of synthesis experiments between 20 and 95 GPa at 650(±50) °C and between 1200 to 2300 °C, using electrically- and laser-heated diamond anvil cells, respectively. Potassium feldspar transformed to a hollandite-type structure in the experimental pressure range from 20 to 95 GPa at temperatures between 1200 to 2300 °C, whereas it remained amorphous at 65(±5) GPa and 650(±50) °C. KAISi3O8 hollandite is, therefore, a stable phase under the pressure and temperature conditions of at least 2200 km deep in the lower mantle and could be an important host for potassium in that region.
|
|
| 3. |
- Dubrovinsky, L., et al.
(author)
-
Noblest of all metals is structurally unstable at high pressure
- 2007
-
In: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 98:4
-
Journal article (peer-reviewed)abstract
- In a series of experiments in externally electrically heated diamond anvil cells we demonstrate that at pressures above similar to 240 GPa gold adopts a hexagonal-close-packed structure. Ab initio calculations predict that at pressures about 250 GPa different stacking sequences of close-packed atomic layers in gold become virtually degenerate in energy, strongly supporting the experimental observations.
|
|
| 4. |
- Fedotenko, T., et al.
(author)
-
Isothermal equation of state of crystalline and glassy materials from optical measurements in diamond anvil cells
- 2021
-
In: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 92:6
-
Journal article (peer-reviewed)abstract
- Here, we present a method to study the equation of state of opaque amorphous and crystalline materials in diamond anvil cells. The approach is based on measurements of sample dimensions using high-resolution optical microscopy. Data on the volumetric strain as a function of pressure allow deriving the isothermal equation of state of the studied material. The analysis of optical images is fully automatized and allows measuring the sample dimensions with the precision of about 60 nm. The methodology was validated by studying isothermal compression of omega-Ti up to 30 GPa in a Ne pressure transmitting medium. Within the accuracy of the measurements, the bulk modulus of omega-Ti determined using optical microscopy was similar to that obtained from x-ray diffraction. For glassy carbon compressed to similar to 30 GPa, the previously unknown bulk modulus was found to be equal to K-0 = 28 (2) GPa [K = 5.5(5)]. Published under an exclusive license by AIP Publishing.
|
|
| 5. |
- Fedotenko, T., et al.
(author)
-
Synthesis of palladium carbides and palladium hydride in laser heated diamond anvil cells
- 2020
-
In: Journal of Alloys and Compounds. - : ELSEVIER SCIENCE SA. - 0925-8388 .- 1873-4669. ; 844
-
Journal article (peer-reviewed)abstract
- The diamond anvil cell (DAC) technique is a powerful method for the synthesis and studying of novel materials at extreme conditions. In this work we report on high-pressure high-temperature (HPHT) synthesis of palladium carbides (PdCx) and palladium hydride (PdH) in a laser heated diamond anvil cell. Formation of PdCx with a face-centered cubic (fcc) structure resulted from a chemical reaction of Pd with carbon from the diamond anvils at a pressure of about 50 GPa and temperature of 2500-3000 K. The samples were analyzed in situ using synchrotron X-ray diffraction. The compressional behavior of PdC0.19(3) and PdC0.17(3), was studied on decompression. The fit of the pressure-volume data using the 3rd order Birch-Murnaghan equation of state gave the following parameters: V-0 = 65.1 (1) angstrom 3, K-0 = 241 (9) GPa and K-0 = 2.1 (3) for PdC0.19(3), and V-0 = 64.51 (5) angstrom(3), K-0 = 189 (8) GPa and K-0 = 4.5 (4) for PdC0.17(3). The palladium hydride PdH was synthesized at P = 39 (2) GPa and T = 1500 (200) K through a direct reaction of Pd with paraffin oil. (C) 2020 Elsevier B.V. All rights reserved.
|
|
| 6. |
- Glazyrin, K., et al.
(author)
-
Sub-micrometer focusing setup for high-pressure crystallography at the Extreme Conditions beamline at PETRA III
- 2022
-
In: Journal of Synchrotron Radiation. - Chichester, United Kingdom : Wiley-Blackwell. - 0909-0495 .- 1600-5775. ; 29, s. 654-663
-
Journal article (peer-reviewed)abstract
- Scientific tasks aimed at decoding and characterizing complex systems and processes at high pressures set new challenges for modern X-ray diffraction instrumentation in terms of X-ray flux, focal spot size and sample positioning. Presented here are new developments at the Extreme Conditions beamline (P02.2, PETRA III, DESY, Germany) that enable considerable improvements in data collection at very high pressures and small scattering volumes. In particular, the focusing of the X-ray beam to the sub-micrometer level is described, and control of the aberrations of the focusing compound refractive lenses is made possible with the implementation of a correcting phase plate. This device provides a significant enhancement of the signal-to-noise ratio by conditioning the beam shape profile at the focal spot. A new sample alignment system with a small sphere of confusion enables single-crystal data collection from grains of micrometer to sub-micrometer dimensions subjected to pressures as high as 200 GPa. The combination of the technical development of the optical path and the sample alignment system contributes to research and gives benefits on various levels, including rapid and accurate diffraction mapping of samples with sub-micrometer resolution at multimegabar pressures.
|
|
| 7. |
- Golosova, N. O., et al.
(author)
-
Magnetic and structural properties of FeCO3 at high pressures
- 2017
-
In: Physical Review B. - : AMER PHYSICAL SOC. - 2469-9950 .- 2469-9969. ; 96:13
-
Journal article (peer-reviewed)abstract
- The structural and magnetic properties of siderite FeCO3 have been studied by means of neutron powder diffraction at pressures up to 7.5 GPa and first-principles theoretical calculations. The lattice compression in the rhombohedral calcite-type structure is dominated by the reduction of the Fe-O bonds, while the changes of the C-O bonds are much less pronounced. The Neel temperature of the antiferromagnetic ( AFM) ground state increases substantially under pressure with a coefficient dT(N)/dP = 1.8K/GPa, which is about 1.5 times larger in comparison with those predicted by the empirical Bloch rule. The ab initio calculations were performed in the framework of the density functional theory including Hubbard-U correction. The calculated structural parameters and Neel temperature as functions of pressure provide a reasonable agreement with the experimental results. The analysis of the density of electronic states points toward increased covalent bonding between the Fe and O atoms upon pressure, giving rise to unexpectedly large pressure coefficient of the Neel temperature and reduced ordered magnetic moments of Fe atoms.
|
|
| 8. |
|
|
| 9. |
- Koemets, E., et al.
(author)
-
Revealing the Complex Nature of Bonding in the Binary High-Pressure Compound FeO2
- 2021
-
In: Physical Review Letters. - : AMER PHYSICAL SOC. - 0031-9007 .- 1079-7114. ; 126:10
-
Journal article (peer-reviewed)abstract
- Extreme pressures and temperatures are known to drastically affect the chemistry of iron oxides, resulting in numerous compounds forming homologous series nFeOmFe(2)O(3) and the appearance of FeO2. Here, based on the results of in situ single-crystal x-ray diffraction, Mossbauer spectroscopy, x-ray absorption spectroscopy, and density-functional theory + dynamical mean-field theory calculations, we demonstrate that iron in high-pressure cubic FeO2 and isostructural FeO2H0.5 is ferric (Fe3+), and oxygen has a formal valence less than 2. Reduction of oxygen valence from 2, common for oxides, down to 1.5 can be explained by a formation of a localized hole at oxygen sites.
|
|
| 10. |
|
|
| 11. |
|
|
| 12. |
|
|
| 13. |
|
|
| 14. |
|
|
| 15. |
- Dubrovinsky, L, et al.
(author)
-
Pressure-induced invar effect in Fe-Ni alloys
- 2001
-
In: PHYSICAL REVIEW LETTERS. - 0031-9007. ; 86:21, s. 4851-4854
-
Journal article (peer-reviewed)abstract
- We have measured the pressure-volume (P-V) relations for cubic iron-nickel alloys for three different compositions: Fe0.64Ni0.36, Fe0.55Ni0.45, and Fe0.20Ni0.80. It is observed that for a certain pressure range the bulk modulus does not change or can even
|
|
| 16. |
|
|
| 17. |
- Dubrovinsky, L. S., et al.
(author)
-
Materials science - The hardest known oxide
- 2001
-
In: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 410:6829, s. 653-654
-
Journal article (peer-reviewed)
|
|
| 18. |
|
|
| 19. |
|
|
| 20. |
|
|
| 21. |
- Kantor, I, et al.
(author)
-
Short-range order and Fe clustering in Mg1-xFexO under high pressure
- 2009
-
In: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 80:1, s. 014204-
-
Journal article (peer-reviewed)abstract
- By combining high-pressure and high-temperature Moumlssbauer spectroscopic studies of (Mg,Fe)O with results of ab initio simulations, several important properties of this material were established. Under high pressure (Mg,Fe)O shows changes in the short-range order with the tendency to form iron clusters. These changes were found to be irreversible, implying sluggish kinetics of these processes at ambient conditions. The pressure-induced spin crossover is interpreted here as a gradual noncooperative transition. The onset and width of spin crossover depends, therefore, not only on pressure, temperature, and composition, but also on short-range order in the FeO-MgO solid solution.
|
|
| 22. |
|
|
| 23. |
- Mattesini, M., et al.
(author)
-
Cubic TiO2 as a potential light absorber in solar-energy conversion
- 2004
-
In: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 70:11
-
Journal article (peer-reviewed)abstract
- Materials are currently sought for use in the photo-induced decomposition of water on crystalline electrodes. Titanium dioxide is valuable in this respect. The electronic structural properties of cubic TiO2 polymorphs were investigated by means of first-principles methods. We demonstrate that both fluorite- and pyrite-type TiO2 have important optical absorptive transitions in the region of the visible light. A cubic TiO2 phase that can efficiently absorb the sunlight would be an important candidate material for the development of the solar cells. Also, we present results on the Ti L edges for the two different titania forms. We predict that a qualitative spectroscopic discrimination of the cubic polymorphs can be achieved by following the Ti 2p → 3d x-ray transitions.
|
|
| 24. |
|
|
| 25. |
|
|
| 26. |
- Norrby, Niklas, et al.
(author)
-
High pressure and high temperature stabilization of cubic AlN in Ti0.60Al0.40N
- 2013
-
In: Journal of Applied Physics. - : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 113:5
-
Journal article (peer-reviewed)abstract
- In the present work, the decomposition of unstable arc evaporated Ti0.6Al0.4N at elevated temperatures and quasihydrostatic pressures has been studied both experimentally and by first-principles calculations. High pressure and high temperature (HPHT) treatment of the samples was realized using the multi anvil press and diamond anvil cell techniques. The products of the HPHT treatment of Ti0.6Al0.4N were investigated using x-ray diffractometry and transmission electron microscopy. Complimentary calculations show that both hydrostatic pressure and high temperature stabilize the cubic phase of AlN, which is one of the decomposition products of Ti0.6Al0.4N. This is in agreement with the experimental results which in addition suggest that the presence of Ti in the system serves to increase the stability region of the cubic c-AlN phase. The results are industrially important as they show that Ti0.6Al0.4N coatings on cutting inserts do not deteriorate faster under pressure due to the cubic AlN to hexagonal AlN transformation.
|
|
| 27. |
- Potapkin, V., et al.
(author)
-
Magnetic interactions in NiO at ultrahigh pressure
- 2016
-
In: PHYSICAL REVIEW B. - : AMER PHYSICAL SOC. - 2469-9950. ; 93:20, s. 201110-
-
Journal article (peer-reviewed)abstract
- Magnetic properties of NiO have been studied in the multimegabar pressure range by nuclear forward scattering of synchrotron radiation using the 67.4 keV Mossbauer transition of Ni-61. The observed magnetic hyperfine splitting confirms the antiferromagnetic state of NiO up to 280 GPa, the highest pressure where magnetism has been observed so far, in any material. Remarkably, the hyperfine field increases from 8.47 T at ambient pressure to similar to 24 T at the highest pressure, ruling out the possibility of a magnetic collapse. A joint x-ray diffraction and extended x-ray-absorption fine structure investigation reveals that NiO remains in a distorted sodium chloride structure in the entire studied pressure range. Ab initio calculations support the experimental observations, and further indicate a complete absence of Mott transition in NiO up to at least 280 GPa.
|
|
| 28. |
|
|
| 29. |
|
|
| 30. |
|
|
| 31. |
|
|
| 32. |
|
|
| 33. |
- Talyzin, A V, et al.
(author)
-
Superhard and superelastic films of polymeric C60
- 2001
-
In: Diamond and related materials. - 0925-9635 .- 1879-0062. ; 10:11, s. 2044-2048
-
Journal article (peer-reviewed)abstract
- The C60 thin film deposited on steel substrate was transformed by high pressure-high temperature treatment to a superhard and superclastic material. The films were studied by Raman spectroscopy in situ at 20 GPa after heating at 300░C and ex situ after the quenching. The hardness and elastic properties of the high-pressure phases have been characterized with nanoindentation. The hardness of the films were determined to be 0.5 ▒ 0.1 GPa and 61.9 ▒ 9 GPa for unmodified C60 and HPHT treated films, respectively. The hardness of the pressurized film is higher than for cubic BN but lower than hardness values reported for ultrahard fullerite samples prepared from powders. An interesting observation was that the HPHT treated film showed an extreme elastic response with an elastic recovery of approximately 90%. ⌐ 2001 Elsevier Science B.V. All rights reserved.
|
|
| 34. |
|
|
