| 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. |
- 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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| 3. |
- 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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| 4. |
- 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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| 5. |
- 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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| 6. |
- Laniel, Dominique, et al.
(författare)
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High-Pressure Synthesis of the beta-Zn3N2 Nitride and the alpha-ZnN4 and beta-ZnN4 Polynitrogen Compounds
- 2021
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Ingår i: Inorganic Chemistry. - : AMER CHEMICAL SOC. - 0020-1669 .- 1520-510X. ; 60:19, s. 14594-14601
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Tidskriftsartikel (refereegranskat)abstract
- High-pressure nitrogen chemistry has expanded at a formidable rate over the past decade, unveiling the chemical richness of nitrogen. Here, the Zn-N system is investigated in laser-heated diamond anvil cells by synchrotron powder and single-crystal X-ray diffraction, revealing three hitherto unobserved nitrogen compounds: beta-Zn3N2, alpha-ZnN4, and beta-ZnN4, formed at 35.0, 63.5, and 81.7 GPa, respectively. Whereas beta-Zn3N2 contains the N3- nitride, both ZnN4 solids are found to be composed of polyacetylene-like [N-4](infinity)(2-) chains. Upon the decompression of beta-ZnN4 below 72.7 GPa, a first-order displacive phase transition is observed from beta-ZnN4 to alpha-ZnN4. The alpha-ZnN4 phase is detected down to 11.0 GPa, at lower pressures decomposing into the known alpha-Zn3N2 (space group Ia (3) over bar) and N-2. The equations of states of beta-ZnN4 and alpha-ZnN4 are also determined, and their bulk moduli are found to be K-0 = 126(9) GPa and K-0 = 76(12) GPa, respectively. Density functional theory calculations were also performed and provide further insight into the Zn-N system. Moreover, comparing the Mg-N and Zn-N systems underlines the importance of minute chemical differences between metal cations in the resulting synthesized phases.
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| 7. |
- Laniel, Dominique, et al.
(författare)
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Nitrosonium nitrate (NO+NO3-) structure solution using in situ single-crystal X-ray diffraction in a diamond anvil cell
- 2021
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Ingår i: IUCrJ. - : International Union of Crystallography. - 2052-2525. ; 8, s. 208-214
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Tidskriftsartikel (refereegranskat)abstract
- At high pressures, autoionization - along with polymerization and metallization - is one of the responses of simple molecular systems to a rise in electron density. Nitrosonium nitrate (NO+NO3-), known for this property, has attracted a large interest in recent decades and was reported to be synthesized at high pressure and high temperature from a variety of nitrogen-oxygen precursors, such as N2O4, N2O and N-2-O-2 mixtures. However, its structure has not been determined unambiguously. Here, we present the first structure solution and refinement for nitrosonium nitrate on the basis of single-crystal X-ray diffraction at 7.0 and 37.0 GPa. The structure model (P2(1)/m space group) contains the triple-bonded NO+ cation and the NO3- sp(2)-trigonal planar anion. Remarkably, crystal-chemical considerations and accompanying density-functional-theory calculations show that the oxygen atom of the NO+ unit is positively charged - a rare occurrence when in the presence of a less-electronegative element.
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