| 1. |
- Aslandukov, Andrey, et al.
(författare)
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Anionic N18 Macrocycles and a Polynitrogen Double Helix in Novel Yttrium Polynitrides YN6 and Y2N11 at 100 GPa
- 2022
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Ingår i: Angewandte Chemie International Edition. - Weinheim, Germany : Wiley-VCH Verlagsgesellschaft. - 1433-7851 .- 1521-3773. ; 61:34
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Tidskriftsartikel (refereegranskat)abstract
- Two novel yttrium nitrides, YN6 and Y2N11, were synthesized by direct reaction between yttrium and nitrogen at 100 GPa and 3000 K in a laser-heated diamond anvil cell. High-pressure synchrotron single-crystal X-ray diffraction revealed that the crystal structures of YN6 and Y2N11 feature a unique organization of nitrogen atoms-a previously unknown anionic N-18 macrocycle and a polynitrogen double helix, respectively. Density functional theory calculations, confirming the dynamical stability of the YN6 and Y2N11 compounds, show an anion-driven metallicity, explaining the unusual bond orders in the polynitrogen units. As the charge state of the polynitrogen double helix in Y2N11 is different from that previously found in Hf2N11 and because N-18 macrocycles have never been predicted or observed, their discovery significantly extends the chemistry of polynitrides.
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| 2. |
- Aslandukov, Andrey, et al.
(författare)
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Stabilization of N6 and N8 anionic units and 2D polynitrogen layers in high-pressure scandium polynitrides
- 2024
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Ingår i: Nature Communications. - : NATURE PORTFOLIO. - 2041-1723. ; 15:1
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Tidskriftsartikel (refereegranskat)abstract
- Nitrogen catenation under high pressure leads to the formation of polynitrogen compounds with potentially unique properties. The exploration of the entire spectrum of poly- and oligo-nitrogen moieties is still in its earliest stages. Here, we report on four novel scandium nitrides, Sc2N6, Sc2N8, ScN5, and Sc4N3, synthesized by direct reaction between yttrium and nitrogen at 78-125 GPa and 2500 K in laser-heated diamond anvil cells. High-pressure synchrotron single-crystal X-ray diffraction reveals that in the crystal structures of the nitrogen-rich Sc2N6, Sc2N8, and ScN5 phases nitrogen is catenated forming previously unknown N-6(6)- and N-8(6)- units and infinity 2(N-5(3-)) anionic corrugated 2D-polynitrogen layers consisting of fused N-12 rings. Density functional theory calculations, confirming the dynamical stability of the synthesized compounds, show that Sc2N6 and Sc2N8 possess an anion-driven metallicity, while ScN5 is an indirect semiconductor. Sc2N6, Sc2N8, and ScN5 solids are promising high-energy-density materials with calculated volumetric energy density, detonation velocity, and detonation pressure higher than those of TNT.
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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. |
- Dubrovinsky, Leonid, et al.
(författare)
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Materials synthesis at terapascal static pressures
- 2022
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Ingår i: Nature. - London, United Kingdom : Nature Publishing Group. - 0028-0836 .- 1476-4687. ; 605:7909, s. 274-278
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Tidskriftsartikel (refereegranskat)abstract
- Theoretical modelling predicts very unusual structures and properties of materials at extreme pressure and temperature conditions(1,2). Hitherto, their synthesis and investigation above 200 gigapascals have been hindered both by the technical complexity of ultrahigh-pressure experiments and by the absence of relevant in situ methods of materials analysis. Here we report on a methodology developed to enable experiments at static compression in the terapascal regime with laser heating. We apply this method to realize pressures of about 600 and 900 gigapascals in a laser-heated double-stage diamond anvil cell(3), producing a rhenium-nitrogen alloy and achieving the synthesis of rhenium nitride Re7N3-which, as our theoretical analysis shows, is only stable under extreme compression. Full chemical and structural characterization of the materials, realized using synchrotron single-crystal X-ray diffraction on microcrystals in situ, demonstrates the capabilities of the methodology to extend high-pressure crystallography to the terapascal regime.
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| 5. |
- Laniel, Dominique, et al.
(författare)
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Aromatic hexazine [N6]4− anion featured in the complex structure of the high-pressure potassium nitrogen compound K9N56
- 2023
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Ingår i: Nature Chemistry. - : NATURE PORTFOLIO. - 1755-4330 .- 1755-4349. ; 15:5, s. 641-646
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Tidskriftsartikel (refereegranskat)abstract
- The recent high-pressure synthesis of pentazolates and the subsequent stabilization of the aromatic [N-5](-) anion at atmospheric pressure have had an immense impact on nitrogen chemistry. Other aromatic nitrogen species have also been actively sought, including the hexaazabenzene N-6 ring. Although a variety of configurations and geometries have been proposed based on ab initio calculations, one that stands out as a likely candidate is the aromatic hexazine anion [N-6](4-). Here we present the synthesis of this species, realized in the high-pressure potassium nitrogen compound K9N56 formed at high pressures (46 and 61 GPa) and high temperature (estimated to be above 2,000 K) by direct reaction between nitrogen and KN3 in a laser-heated diamond anvil cell. The complex structure of K9N56-composed of 520 atoms per unit cell-was solved based on synchrotron single-crystal X-ray diffraction and corroborated by density functional theory calculations. The observed hexazine anion [N-6](4-) is planar and proposed to be aromatic.
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| 6. |
- Laniel, Dominique, et al.
(författare)
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Front Cover: Revealing Phosphorus Nitrides up to the Megabar Regime: Synthesis of α′-P3N5, δ-P3N5 and PN2 (Chem. Eur. J. 62/2022)
- 2022
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Ingår i: Chemistry - A European Journal. - : Wiley-VCH Verlagsgesellschaft. - 0947-6539 .- 1521-3765. ; 28:62
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- For the last 30 years, the lack of a binary phosphorus nitride containing PN6 octahedra formed a scientific chasm between carbon-group and oxygen-group nitrides, both featuring a variety of solids with XN6 units (X being a non-metal element). Now, the discovery of the δ-P3N5 and PN2 phosphorus nitrides—formed under high pressure and both composed of the elusive PN6 octahedron—builds a long-sought-after bridge between these two groups of nitrides. More information can be found in the Research Article by D. Laniel, F. Trybel, and co-workers (DOI: 10.1002/chem.202201998).
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| 7. |
- Laniel, Dominique, et al.
(författare)
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Revealing Phosphorus Nitrides up to the Megabar Regime: Synthesis of α′‐P3N5, δ‐P3N5 and PN2
- 2022
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Ingår i: Chemistry - A European Journal. - : WILEY-V C H VERLAG GMBH. - 0947-6539 .- 1521-3765. ; 28:62
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Tidskriftsartikel (refereegranskat)abstract
- Non-metal nitrides are an exciting field of chemistry, featuring a significant number of compounds that can possess outstanding material properties. These properties mainly rely on maximizing the number of strong covalent bonds, with crosslinked XN6 octahedra frameworks being particularly attractive. In this study, the phosphorus-nitrogen system was studied up to 137 GPa in laser-heated diamond anvil cells, and three previously unobserved phases were synthesized and characterized by single-crystal X-ray diffraction, Raman spectroscopy measurements and density functional theory calculations. delta-P3N5 and PN2 were found to form at 72 and 134 GPa, respectively, and both feature dense 3D networks of the so far elusive PN6 units. The two compounds are ultra-incompressible, having a bulk modulus of K-0=322 GPa for delta-P3N5 and 339 GPa for PN2. Upon decompression below 7 GPa, delta-P3N5 undergoes a transformation into a novel alpha -P3N5 solid, stable at ambient conditions, that has a unique structure type based on PN4 tetrahedra. The formation of alpha -P3N5 underlines that a phase space otherwise inaccessible can be explored through materials formed under high pressure.
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| 8. |
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| 9. |
- Liang, Akun, et al.
(författare)
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High-Pressure Synthesis of Ultra-Incompressible, Hard and Superconducting Tungsten Nitrides
- 2024
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Ingår i: Advanced Functional Materials. - : WILEY-V C H VERLAG GMBH. - 1616-301X .- 1616-3028.
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Tidskriftsartikel (refereegranskat)abstract
- Transition metal nitrides, particularly those of 5d metals, are known for their outstanding properties, often relevant for industrial applications. Among these metal elements, tungsten is especially attractive given its low cost. In this high-pressure investigation of the W-N system, two novel ultra-incompressible tungsten nitride superconductors, namely W2N3 and W3N5, are successfully synthesized at 35 and 56 GPa, respectively, through a direct reaction between N2 and W in laser-heated diamond anvil cells. Their crystal structure is determined using synchrotron single-crystal X-ray diffraction. While the W2N3 solid's sole constituting nitrogen species are N3- units, W3N5 features both discrete N3- as well as N24- pernitride anions. The bulk modulus of W2N3 and W3N5 is experimentally determined to be 380(3) and 406(7) GPa, and their ultra-incompressible behavior is rationalized by their constituting WN7 polyhedra and their linkages. Importantly, both W2N3 and W3N5 are recoverable to ambient conditions and stable in air. Density functional theory calculations reveal W2N3 and W3N5 to have a Vickers hardness of 30 and 34 GPa, and superconducting transition temperatures at ambient pressure (50 GPa) of 11.6 K (9.8 K) and 9.4 K (7.2 K), respectively. Additionally, transport measurements performed at 50 GPa on W2N3 corroborate with the calculations. Two recoverable tungsten nitrides, namely W2N3 and W3N5, are synthesized using laser-heated diamond anvil cells. Both compounds exhibit a high bulk modulus, hardness, and superconducting transition temperature. image
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| 10. |
- Morana, Marta, et al.
(författare)
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Cubic or Not Cubic? Combined Experimental and Computational Investigation of the Short-Range Order of Tin Halide Perovskites
- 2023
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Ingår i: Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185. ; 14, s. 2178-2186
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Tidskriftsartikel (refereegranskat)abstract
- Tin-based metal halide perovskites with a composition of ASnX3 (where A= MA or FA and X = I or Br) have been investigated by means of X-ray total scattering techniques coupled to pair distribution function (PDF) analysis. These studies revealed that that none of the four perovskites has a cubic symmetry at the local scale and that a degree of increasing distortion is always present, in particular when the cation size is increased, i.e., from MA to FA, and the hardness of the anion is increased, i.e., from Br- to I-. Electronic structure calculations provided good agreement with experimental band gaps for the four perovskites when local dynamical distortions were included in the calculations. The averaged structure obtained from molecular dynamics simulations was consistent with experimental local structures determined via X-ray PDF, thus highlighting the robustness of computational modeling and strengthening the correlation between experimental and computational results.
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