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| 2. |
- Bocharov, D., et al.
(författare)
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Electronic structure of cubic ScF3 from first-principles calculations
- 2016
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Ingår i: Low temperature physics (Woodbury, N.Y., Print). - : AIP Publishing. - 1063-777X .- 1090-6517. ; 42:7, s. 556-560
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Tidskriftsartikel (refereegranskat)abstract
- The ground state properties of cubic scandium trifluoride (ScF3) perovskite were studied using first-principles calculations. The electronic structure of ScF3 was determined by linear combination of atomic orbital (LCAO) and plane wave projector augmented-wave (PAW) methods using modified hybrid exchange-correlation functionals within the density functional theory (DFT). The comprehensive comparison of the results obtained by two methods is presented. Both methods allowed us to reproduce the lattice constant found experimentally in ScF3 at low temperatures and to predict its electronic structure in good agreement with known experimental valence-band photoelectron and F 1s x-ray absorption spectra.
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| 3. |
- Chesnokov, A., et al.
(författare)
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The local atomic structure and thermoelectric properties of Ir-doped ZnO : hybrid DFT calculations and XAS experiments
- 2021
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Ingår i: Journal of Materials Chemistry C. - : Royal Society of Chemistry. - 2050-7526 .- 2050-7534. ; 9:14, s. 4948-4960
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Tidskriftsartikel (refereegranskat)abstract
- We combined the hybrid density functional theory (DFT) calculations and X-ray absorption spectroscopy (XAS) experiments in the study of the local atomic structure around Ir ions in ZnO thin films with different iridium content. This was then used in the first principles analysis of the thermoelectric properties of material. The emphasis has been put on the conditions for a positive Seebeck coefficient and p-type electrical conductivity as the functions of the Fermi level. We studied both computationally and experimentally several possible IrOxpolyhedra (complexes) with a different number of surrounding oxygens and Ir oxidation states, including those with the formation of peroxide ions (O22−). In particular, octahedral coordination of iridium ions was identified by reverse Monte Carlo (RMC) simulations of the Ir L3-edge EXAFS spectra of ZnO:Ir thin films as the predominant complex, which is supported by the calculated lowest interstitial oxygen incorporation energies. All the calculated IrOx(x= 4, 5, 6) complexes, regardless of Ir the oxidation state, demonstrate potential for p-type conduction if the Fermi level (μF) falls in the range of 0-0.8 eV from the valence band maximum (VBM) and the Ir concentration is high enough (12.5% in the present DFT calculations). Even though the corresponding calculated Seebeck coefficient (S) around 80-89 μV K−1slightly exceeds the experimental values, we emphasise the presence of an important plateau in the dependence ofSonμFin this range for two complexes with the formation of peroxide ions (O22−). We predicted also that peroxide ions O22−are characterized by the calculated phonon frequencies of 810-942 cm−1in agreement with our previous Raman experimental results. In this light, we discuss the high sensitivity of calculatedS(μF) dependences to the atomic and electronic structure.
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| 4. |
- Green, Sara, et al.
(författare)
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Structure and composition of sputter-deposited nickel-tungsten oxide films
- 2011
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Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 519:7, s. 2062-2066
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Tidskriftsartikel (refereegranskat)abstract
- Films of mixed nickel-tungsten oxide, denoted NixW1-x oxide, were prepared by reactive DC magnetron co-sputtering from metallic targets and were characterized by Rutherford backscattering spectrometry. X-ray photoelectron spectroscopy, X-ray diffractometry and Raman spectroscopy. A consistent picture of the structure and composition emerged, and at x<0.50 the films comprised a mixture of amorphous WO3 and nanosized NiWO4, at x = 0.50 the nanosized NiWO4 phase was dominating, and at x>0.50 the films contained nanosized NiO and NiWO4.
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| 5. |
- Purans, J., et al.
(författare)
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Local electronic structure rearrangements and strong anharmonicity in YH3 under pressures up to 180 GPa
- 2021
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- The discovery of superconductivity above 250 K at high pressure in LaH10 and the prediction of overcoming the room temperature threshold for superconductivity in YH10 urge for a better understanding of hydrogen interaction mechanisms with the heavy atom sublattice in metal hydrides under high pressure at the atomic scale. Here we use locally sensitive X-ray absorption fine structure spectroscopy (XAFS) to get insight into the nature of phase transitions and the rearrangements of local electronic and crystal structure in archetypal metal hydride YH3 under pressure up to 180 GPa. The combination of the experimental methods allowed us to implement a multiscale length study of YH3: XAFS (short-range), Raman scattering (medium-range) and XRD (long-range). XANES data evidence a strong effect of hydrogen on the density of 4d yttrium states that increases with pressure and EXAFS data evidence a strong anharmonicity, manifested as yttrium atom vibrations in a double-well potential.
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| 6. |
- Purans, J, et al.
(författare)
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X-ray absorption study of Ce-Ti oxide films
- 2001
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Ingår i: ELECTROCHIMICA ACTA. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0013-4686. ; 46:13-14, s. 2055-2058
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Tidskriftsartikel (refereegranskat)abstract
- X-ray absorption measurements at the Ce L-3 L-1 and Ti K-edges have been done to study local structure and electronic properties of CeO2-TiO2 thin films produced by reactive d.c. magnetron sputtering. The local environment around titanium and cerium ions
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