| 1. |
- Koemets, E., et al.
(author)
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Revealing the Complex Nature of Bonding in the Binary High-Pressure Compound FeO2
- 2021
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In: Physical Review Letters. - : AMER PHYSICAL SOC. - 0031-9007 .- 1079-7114. ; 126:10
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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.
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| 2. |
- Bruening, Lukas, et al.
(author)
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Stabilization of Guanidinate Anions [CN3]5− in Calcite-Type SbCN3
- 2023
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In: Angewandte Chemie International Edition. - : WILEY-V C H VERLAG GMBH. - 1433-7851 .- 1521-3773. ; 62:47
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Journal article (peer-reviewed)abstract
- The stabilization of nitrogen-rich phases presents a significant chemical challenge due to the inherent stability of the dinitrogen molecule. This stabilization can be achieved by utilizing strong covalent bonds in complex anions with carbon, such as cyanide CN- and NCN(2- )carbodiimide, while more nitrogen-rich carbonitrides are hitherto unknown. Following a rational chemical design approach, we synthesized antimony guanidinate SbCN3 at pressures of 32-38 GPa using various synthetic routes in laser-heated diamond anvil cells. SbCN3, which is isostructural to calcite CaCO3, can be recovered under ambient conditions. Its structure contains the previously elusive guanidinate anion [CN3](5-), marking a fundamental milestone in carbonitride chemistry. The crystal structure of SbCN3 was solved and refined from synchrotron single-crystal X-ray diffraction data and was fully corroborated by theoretical calculations, which also predict that SbCN3 has a direct band gap with the value of 2.20 eV. This study opens a straightforward route to the entire new family of inorganic nitridocarbonates.
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| 3. |
- Fedotenko, T., et al.
(author)
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Isothermal equation of state of crystalline and glassy materials from optical measurements in diamond anvil cells
- 2021
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In: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 92:6
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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.
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| 4. |
- Fedotenko, T., et al.
(author)
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Synthesis of palladium carbides and palladium hydride in laser heated diamond anvil cells
- 2020
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In: Journal of Alloys and Compounds. - : ELSEVIER SCIENCE SA. - 0925-8388 .- 1873-4669. ; 844
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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.
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| 5. |
- Glazyrin, K., et al.
(author)
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Sub-micrometer focusing setup for high-pressure crystallography at the Extreme Conditions beamline at PETRA III
- 2022
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In: Journal of Synchrotron Radiation. - Chichester, United Kingdom : Wiley-Blackwell. - 0909-0495 .- 1600-5775. ; 29, s. 654-663
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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.
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