| 1. |
- Aslandukov, Andrey, et al.
(författare)
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High-Pressure Yttrium Nitride, Y5N14, Featuring Three Distinct Types of Nitrogen Dimers
- 2021
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Ingår i: The Journal of Physical Chemistry C. - : AMER CHEMICAL SOC. - 1932-7447 .- 1932-7455. ; 125:32, s. 18077-18084
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Tidskriftsartikel (refereegranskat)abstract
- Yttrium nitride, Y5N14, was synthesized by direct reaction between yttrium and nitrogen at similar to 50 GPa and similar to 2000 K in a laser-heated diamond anvil cell. High-pressure single-crystal X-ray diffraction revealed that the crystal structure of Y5N14 (space group P4/mbm) contains three distinct types of nitrogen dimers. Crystal chemical analysis and ab initio calculations demonstrated that the dimers [N-2](x-) are crystallographically and chemically nonequivalent and possess distinct noninteger formal charges (x) that make Y5N14 unique among known compounds. Theoretical computations showed that Y5N14 has an anion-driven metallicity, with the filled part of its conduction band formed by nitrogen p-states. The compressibility of Y5N14, determined on decompression down to similar to 10 GPa, was found to be uncommonly high for dinitrides containing +3 cations (the bulk modulus K-0 = 137(6) GPa).
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| 2. |
- Aslandukov, Andrey, et al.
(författare)
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Stabilization Of The CN35− Anion In Recoverable High-pressure Ln3O2(CN3) (Ln=La, Eu, Gd, Tb, Ho, Yb) Oxoguanidinates
- 2023
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Ingår i: Angewandte Chemie International Edition. - : WILEY-V C H VERLAG GMBH. - 1433-7851 .- 1521-3773. ; 62:47
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Tidskriftsartikel (refereegranskat)abstract
- A series of isostructural Ln(3)O(2)(CN3) (Ln=La, Eu, Gd, Tb, Ho, Yb) oxoguanidinates was synthesized under high-pressure (25-54 GPa) high-temperature (2000-3000 K) conditions in laser-heated diamond anvil cells. The crystal structure of this novel class of compounds was determined via synchrotron single-crystal X-ray diffraction (SCXRD) as well as corroborated by X-ray absorption near edge structure (XANES) measurements and density functional theory (DFT) calculations. The Ln(3)O(2)(CN3) solids are composed of the hitherto unknown CN35- guanidinate anion-deprotonated guanidine. Changes in unit cell volumes and compressibility of Ln(3)O(2)(CN3) (Ln=La, Eu, Gd, Tb, Ho, Yb) compounds are found to be dictated by the lanthanide contraction phenomenon. Decompression experiments show that Ln(3)O(2)(CN3) compounds are recoverable to ambient conditions. The stabilization of the CN35- guanidinate anion at ambient conditions provides new opportunities in inorganic and organic synthetic chemistry.
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| 3. |
- Aslandukova, Alena, et al.
(författare)
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Diverse high-pressure chemistry in Y-NH3BH3 and Y–paraffin oil systems
- 2024
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Ingår i: Science Advances. - : AMER ASSOC ADVANCEMENT SCIENCE. - 2375-2548. ; 10:11
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Tidskriftsartikel (refereegranskat)abstract
- The yttrium-hydrogen system has gained attention because of near-ambient temperature superconductivity reports in yttrium hydrides at high pressures. We conducted a study using synchrotron single-crystal x-ray diffraction (SCXRD) at 87 to 171 GPa, resulting in the discovery of known (two YH3 phases) and five previously unknown yttrium hydrides. These were synthesized in diamond anvil cells by laser heating yttrium with hydrogen-rich precursors-ammonia borane or paraffin oil. The arrangements of yttrium atoms in the crystal structures of new phases were determined on the basis of SCXRD, and the hydrogen content estimations based on empirical relations and ab initio calculations revealed the following compounds: Y3H11, Y2H9, Y4H23, Y13H75, and Y4H25. The study also uncovered a carbide (YC2) and two yttrium allotropes. Complex phase diversity, variable hydrogen content in yttrium hydrides, and their metallic nature, as revealed by ab initio calculations, underline the challenges in identifying superconducting phases and understanding electronic transitions in high-pressure synthesized materials.
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| 4. |
- Aslandukova, Alena, et al.
(författare)
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High-pressure hP3 yttrium allotrope with CaHg2-type structure as a prototype of the hP3 rare-earth hydride series
- 2023
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Ingår i: Physical Review B. - : AMER PHYSICAL SOC. - 2469-9950 .- 2469-9969. ; 107:1
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Tidskriftsartikel (refereegranskat)abstract
- A high-pressure (HP) yttrium allotrope, hP3-Y (space group P6/mmm), was synthesized in a multi-anvil press at 20 GPa and 2000 K which is recoverable to ambient conditions. Its relative stability and electronic properties were investigated using density functional theory calculations. A hP3-Y derivative hydride, hP3-YHx, with a variable hydrogen content (x = 2.8, 3, 2.4), was synthesized in diamond anvil cells by the direct reaction of yttrium with paraffin oil, hydrogen gas, and ammonia borane upon laser heating to similar to 3000 K at 51, 45 and 38 GPa, respectively. Room-temperature decompression leads to gradual reduction and eventually the complete loss of hydrogen at ambient conditions. Isostructural hP3-NdHx and hP3-GdHx hydrides were synthesized from Nd and Gd metals and paraffin oil, suggesting that the hP3-Y structure type may be common for rare-earth elements. Our results expand the list of allotropes of trivalent lanthanides and their hydrides and suggest that they should be considered in the context of studies of HP behavior and properties of this broad class of materials.
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| 5. |
- Aslandukova, Alena, et al.
(författare)
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Novel High-Pressure Yttrium Carbide gamma-Y4C5 Containing [C-2] and Nonlinear [C-3] Units with Unusually Large Formal Charges
- 2021
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Ingår i: Physical Review Letters. - : AMER PHYSICAL SOC. - 0031-9007 .- 1079-7114. ; 127:13
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Tidskriftsartikel (refereegranskat)abstract
- Changes in the bonding of carbon under high pressure leads to unusual crystal chemistry and can dramatically alter the properties of transition metal carbides. In this work, the new orthorhombic polymorph of yttrium carbide, gamma-Y4C5, was synthesized from yttrium and paraffin oil in a laser-heated diamond anvil cell at similar to 50 GPa. The structure of gamma-Y4C5 was solved and refined using in situ synchrotron single-crystal x-ray diffraction. It includes two carbon groups: [C-2] dimers and nonlinear [C-3] trimers. Crystal chemical analysis and density functional theory calculations revealed unusually high noninteger charges ([C-2](5.2-) and [C-3](6.8-)) and unique bond orders (<1.5). Our results extend the list of possible carbon states at extreme conditions.
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| 6. |
- Bykov, Maxim, et al.
(författare)
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High-Pressure Synthesis of a Nitrogen-Rich Inclusion Compound ReN8·xN2 with Conjugated Polymeric Nitrogen Chains
- 2018
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Ingår i: Angewandte Chemie International Edition. - : WILEY-V C H VERLAG GMBH. - 1433-7851 .- 1521-3773. ; 57:29, s. 9048-9053
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Tidskriftsartikel (refereegranskat)abstract
- A nitrogen-rich compound, ReN(8)xN(2), was synthesized by a direct reaction between rhenium and nitrogen at high pressure and high temperature in a laser-heated diamond anvil cell. Single-crystal X-ray diffraction revealed that the crystal structure, which is based on the ReN8 framework, has rectangular-shaped channels that accommodate nitrogen molecules. Thus, despite a very high synthesis pressure, exceeding 100GPa, ReN(8)xN(2) is an inclusion compound. The amount of trapped nitrogen (x) depends on the synthesis conditions. The polydiazenediyl chains [-N=N-] that constitute the framework have not been previously observed in any compound. Abinitio calculations on ReN(8)xN(2) provide strong support for the experimental results and conclusions.
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| 7. |
- Bykov, Maxim, et al.
(författare)
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High-Pressure Synthesis of Dirac Materials: Layered van der Waals Bonded BeN4 Polymorph
- 2021
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Ingår i: Physical Review Letters. - : AMER PHYSICAL SOC. - 0031-9007 .- 1079-7114. ; 126:17
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Tidskriftsartikel (refereegranskat)abstract
- High-pressure chemistry is known to inspire the creation of unexpected new classes of compounds with exceptional properties. Here, we employ the laser-heated diamond anvil cell technique for synthesis of a Dirac material BeN4. A triclinic phase of beryllium tetranitride tr-BeN4 was synthesized from elements at similar to 85 GPa. Upon decompression to ambient conditions, it transforms into a compound with atomic-thick BeN4 layers interconnected via weak van der Waals bonds and consisting of polyacetylene-like nitrogen chains with conjugated pi systems and Be atoms in square-planar coordination. Theoretical calculations for a single BeN4 layer show that its electronic lattice is described by a slightly distorted honeycomb structure reminiscent of the graphene lattice and the presence of Dirac points in the electronic band structure at the Fermi level. The BeN4 layer, i.e., beryllonitrene, represents a qualitatively new class of 2D materials that can be built of a metal atom and polymeric nitrogen chains and host anisotropic Dirac fermions.
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| 8. |
- Bykov, Maxim, et al.
(författare)
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Realization of an Ideal Cairo Tessellation in Nickel Diazenide NiN2: High-Pressure Route to Pentagonal 2D Materials
- 2021
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Ingår i: ACS Nano. - : AMER CHEMICAL SOC. - 1936-0851 .- 1936-086X. ; 15:8, s. 13539-13546
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Tidskriftsartikel (refereegranskat)abstract
- Most of the studied two-dimensional (2D) materials are based on highly symmetric hexagonal structural motifs. In contrast, lower-symmetry structures may have exciting anisotropic properties leading to various applications in nano-electronics. In this work we report the synthesis of nickel diazenide NiN2 which possesses atomic-thick layers comprised of Ni2N3 pentagons forming Cairo-type tessellation. The layers of NiN2 are weakly bonded with the calculated exfoliation energy of 0.72 J/m(2), which is just slightly larger than that of graphene. The compound crystallizes in the space group of the ideal Cairo tiling (P4/mbm) and possesses significant anisotropy of elastic properties. The single-layer NiN2 is a direct-band-gap semiconductor, while the bulk material is metallic. This indicates the promise of NiN2 to be a precursor of a pentagonal 2D material with a tunable direct band gap.
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| 9. |
- Dong, Weiwei, et al.
(författare)
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Fe0.79Si0.07B0.14 metallic glass gaskets for high-pressure research beyond 1 Mbar
- 2022
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Ingår i: Journal of Synchrotron Radiation. - : Wiley-Blackwell Publishing Ltd. - 0909-0495 .- 1600-5775. ; 29, s. 1167-1179
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Tidskriftsartikel (refereegranskat)abstract
- A gasket is an important constituent of a diamond anvil cell (DAC) assembly, responsible for the sample chamber stability at extreme conditions for X-ray diffraction studies. In this work, we studied the performance of gaskets made of metallic glass Fe0.79Si0.07B0.14 in a number of high-pressure X-ray diffraction (XRD) experiments in DACs equipped with conventional and toroidal-shape diamond anvils. The experiments were conducted in either axial or radial geometry with X-ray beams of micrometre to sub-micrometre size. We report that Fe0.79Si0.07B0.14 metallic glass gaskets offer a stable sample environment under compression exceeding 1 Mbar in all XRD experiments described here, even in those involving small-molecule gases (e.g. Ne, H-2) used as pressure-transmitting media or in those with laser heating in a DAC. Our results emphasize the materials importance for a great number of delicate experiments conducted under extreme conditions. They indicate that the application of Fe0.79Si0.07B0.14 metallic glass gaskets in XRD experiments for both axial and radial geometries substantially improves various aspects of megabar experiments and, in particular, the signal-to-noise ratio in comparison to that with conventional gaskets made of Re, W, steel or other crystalline metals.
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| 10. |
- Fedotenko, Timofey, et al.
(författare)
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Synthesis and Compressibility of Novel Nickel Carbide at Pressures of Earths Outer Core
- 2021
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Ingår i: Minerals. - : MDPI. - 2075-163X. ; 11:5
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Tidskriftsartikel (refereegranskat)abstract
- We report the high-pressure synthesis and the equation of state (EOS) of a novel nickel carbide (Ni3C). It was synthesized in a diamond anvil cell at 184(5) GPa through a direct reaction of a nickel powder with carbon from the diamond anvils upon heating at 3500 (200) K. Ni3C has the cementite-type structure (Pnma space group, a = 4.519(2) angstrom, b = 5.801(2) angstrom, c = 4.009(3) angstrom), which was solved and refined based on in-situ synchrotron single-crystal X-ray diffraction. The pressure-volume data of Ni3C was obtained on decompression at room temperature and fitted to the 3rd order Burch-Murnaghan equation of state with the following parameters: V-0 = 147.7(8) angstrom(3), K-0 = 157(10) GPa, and K-0 = 7.8(6). Our results contribute to the understanding of the phase composition and properties of Earths outer core.
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