| 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. |
- Trybel, Florian, et al.
(författare)
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Absence of proton tunneling during the hydrogen-bond symmetrization in delta-AlOOH
- 2021
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Ingår i: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 104:10
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Tidskriftsartikel (refereegranskat)abstract
- delta-AlOOH is of significant crystallochemical interest due to a subtle structural transition near 10 GPa from a P2(1) nm to a Pnnm structure, the nature and origin of hydrogen disorder, the symmetrization of the O-H center dot center dot center dot O hydrogen bond and their interplay. We perform a series of density functional theory-based simulations in combination with high-pressure nuclear magnetic resonance (NMR) experiments on delta-AlOOH up to 40 GPa with the goal to better characterize the hydrogen potential and therefore the nature of hydrogen disorder. Simulations predict a phase transition in agreement with our NMR experiments at 10 - 11 GPa and hydrogen bond symmetrization at 14.7 GPa. Calculated hydrogen potentials do not show any double-well character and there is no evidence for proton tunneling in our NMR data.
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