| 1. |
- Ek, Martin, 1984, et al.
(författare)
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Redox dynamics of 2D crystalline vanadium oxide phases on high-index anatase facets
- 2023
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Ingår i: Nanoscale. - 2040-3372 .- 2040-3364. ; 15:21, s. 9503-9509
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Tidskriftsartikel (refereegranskat)abstract
- Vanadium oxides exist in a multitude of phases with varying structure and stoichiometry. This abundance of phases can be extended through the use of other oxides as supports, and through redox treatments. However, the combined effects of different supports and redox treatments can be difficult to identify, particularly when present as different terminating facets on nanoparticles. Here, we examine structural dynamics of 2D vanadium oxides supported on anatase TiO2 nanoparticles, correlated with changes in oxidation state, using in situ transmission electron microscopy imaging and electron energy loss spectroscopy. As the average oxidation state is reduced below V(iv), an ordered cubic V(ii) phase is observed exclusively at the high-index {10l} facets of the support. This local accommodation of highly reduced states is necessary for explaining the observed range of average oxidation states. In turn, the findings show that oxidation states extending from V(v)-V(iv) to V(ii) can be simultaneously stabilized by different supporting oxide surfaces during exposure to atmospheres with controlled redox potential.
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| 2. |
- Langreth, D. C., et al.
(författare)
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A density functional for sparse matter
- 2009
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Ingår i: Journal of Physics Condensed Matter. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 21:8, s. 084203-
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Tidskriftsartikel (refereegranskat)abstract
- Sparse matter is abundant and has both strong local bonds and weak nonbonding forces, in particular nonlocal van der Waals (vdW) forces between atoms separated by empty space. It encompasses a broad spectrum of systems, like soft matter, adsorption systems and biostructures. Density-functional theory (DFT), long since proven successful for dense matter, seems now to have come to a point, where useful extensions to sparse matter are available. In particular, a functional form, vdW-DF (Dion et al 2004 Phys. Rev. Lett. 92 246401; Thonhauser et al 2007 Phys. Rev. B 76 125112), has been proposed for the nonlocal correlations between electrons and applied to various relevant molecules and materials, including to those layered systems like graphite, boron nitride and molybdenum sulfide, to dimers of benzene, polycyclic aromatic hydrocarbons (PAHs), doped benzene, cytosine and DNA base pairs, to nonbonding forces in molecules, to adsorbed molecules, like benzene, naphthalene, phenol and adenine on graphite, alumina and metals, to polymer and carbon nanotube (CNT) crystals, and hydrogen storage in graphite and metal–organic frameworks (MOFs), and to the structure of DNA and of DNA with intercalators. Comparison with results from wavefunction calculations for the smaller systems and with experimental data for the extended ones show the vdW-DF path to be promising. This could have great ramifications.
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| 3. |
- Moses, PG, et al.
(författare)
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Density functional study of the adsorbtion and van der Waals binding of aromatic and conjugated compounds on the basal plane of MoS2
- 2009
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 1089-7690 .- 0021-9606. ; 130:10, s. 104709-
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Tidskriftsartikel (refereegranskat)abstract
- Accurate calculations of adsorption energies of cyclic molecules are of key importance in investigations of, e.g., hydrodesulfurization (HDS) catalysis. The present density functional theory (DFT) study of a set of important reactants, products, and inhibitors in HDS catalysis demonstrates that van der Waals interactions are essential for binding energies on MoS2 surfaces and that DFT with a recently developed exchange-correlation functional (vdW-DF) accurately calculates the van der Waals energy. Values are calculated for the adsorption energies of butadiene, thiophene, benzothiophene, pyridine, quinoline, benzene, and naphthalene on the basal plane of MoS2, showing good agreement with available experimental data, and the equilibrium geometry is found as flat at a separation of about 3.5 Å for all studied molecules. This adsorption is found to be due to mainly van der Waals interactions. Furthermore, the manifold of adsorption-energy values allows trend analyses to be made, and they are found to have a linear correlation with the number of main atoms. © 2009 American Institute of Physics.
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| 4. |
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| 5. |
- Niemi, MEK, et al.
(författare)
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- 2021
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swepub:Mat__t
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