| 1. |
- Ahuja, B. L., et al.
(författare)
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A study of electron momentum density and charge transfer in W-Cu system
- 2009
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Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 467:1-2, s. 595-599
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Tidskriftsartikel (refereegranskat)abstract
- We present the first ever Compton scattering study on WxCu1-x(x=0.60, 0.72) alloys. The Compton profile measurements have been made using 20Ci (CS)-C-137 gamma-ray source. The experimental data are compared with the superposition of APW-based Compton profiles of constituent metals. A schematic study on charge transfer has been reported using the experimental valence band Compton profiles of both the alloys, W and Cu. Our first ever data support the charge transfer from W to Cu on alloying, which is also confirmed by our band structure calculations employing exact muffin-tin orbitals method (EMTO). (C) 2007 Elsevier B.V. All rights reserved.
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| 2. |
- Astrath, N. G. C., et al.
(författare)
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Thermal lens and photoacoustic spectroscopy to determine the thermo-optical properties of semiconductors
- 2005
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Ingår i: Journal de Physique IV. - : EDP Sciences. - 1155-4339 .- 1764-7177. ; 125, s. 181-183
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Tidskriftsartikel (refereegranskat)abstract
- In this work we used photoacoustic and thermal lens spectroscopy to study four different semiconductor samples: PbI2, 4HSiC, NiCrO and NiO. The results showed that the combination of these two techniques provided the values of the band gap energies and the thermal diffusivities.
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| 3. |
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| 4. |
- Heathman, S., et al.
(författare)
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A high-pressure structure in curium linked to magnetism
- 2005
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 309:5731, s. 110-113
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Tidskriftsartikel (refereegranskat)abstract
- Curium ties at the center of the actinide series and has a half-filled shell. with seven 5f electrons spatially residing inside its radon core. As a function of pressure, curium exhibits five different crystallographic phases up to 100 gigapascals, of which all but one are also found in the preceding element, americium. We describe here a structure in curium, Cm III, with monoctinic symmetry, space group C2/c, found at intermediate pressures (between 37 and 56 gigapascals). Ab initio electronic structure calculations agree with the observed sequence of structures and establish that it is the spin polarization of curium's 5f electrons that stabilizes Cm Ill. The results reveal that curium is one of a few elements that has a lattice structure stabilized by magnetism.
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| 5. |
- Ahuja, SK, et al.
(författare)
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A plea for justice for jailed medical workers
- 2006
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Ingår i: Science (New York, N.Y.). - : American Association for the Advancement of Science (AAAS). - 1095-9203 .- 0036-8075. ; 314:5801, s. 924-925
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 6. |
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| 7. |
- Berseth, P. A., et al.
(författare)
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Carbon Nanomaterials as Catalysts for Hydrogen Uptake and Release in NaAlH4
- 2009
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Ingår i: Nano letters (Print). - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 9:4, s. 1501-1505
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Tidskriftsartikel (refereegranskat)abstract
- A synergistic approach involving experiment and first-principles theory not only shows that carbon nanostructures can be used as catalysts for hydrogen uptake and release in complex metal hydrides such as sodium alanate, NaAlH4, but also provides an unambiguous understanding of how the catalysts work. Here we show that the stability of NaAlH4 originates with the charge transfer from Na to the AlH4 moiety, resulting in an ionic bond between Na+ and AlH4- and a covalent bond between Al and H. Interaction of NaAlH4 with an electronegative substrate such as carbon fullerene or nanotube affects the ability of Na to donate its charge to AlH4, consequently weakening the Al-H bond and causing hydrogen to desorb at lower temperatures as well as facilitating the absorption of H-2 to reverse the dehydrogenation reaction. In addition, based on our experimental observations and theoretical calculations it appears the curvature of the carbon nanostructure plays a role in the catalytic process. Ab initio molecular dynamics simulation further reveals the time evolution of the charge transfer process.
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| 8. |
- Dallera, C., et al.
(författare)
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Understanding mixed valent materials : Effects of dynamical core-hole screening in high-pressure x-ray spectroscopy
- 2006
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 74:8, s. 081101-
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Tidskriftsartikel (refereegranskat)abstract
- Changes in the electronic structure of Yb, a material whose valence is modified under pressure, are observed with remarkable detail in x-ray absorption and emission data measured between ambient conditions and 20 GPa. These changes are reproduced by a theory that essentially does not rely on experimental parameters, and includes dynamical core-hole screening. From the combined experimental and theoretical data we can firmly establish on a quantitative level how the valency of an intermediate valence material is modified by pressure. In metallic Yb it increases from 2 to 2.55 +/- 0.05 between 0 and 20 GPa.
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| 9. |
- Dong, C. L., et al.
(författare)
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Electronic structure and surface structure of Cu2S nanorods from polarization dependent X-ray absorption spectroscopy
- 2006
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048 .- 1873-2526. ; 151:1, s. 64-70
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Tidskriftsartikel (refereegranskat)abstract
- Highly aligned CuS nanorods have been studied by polarization dependent X-ray absorption spectroscopy. In contrast to bulk Cu2S, strong s, p, and d hybridization is found in the nanorods. The polarization dependence shows a predominant d(z2) character of Cu 3d states. Ab initio multiple-scattering calculations confirm the strong hybridization, and reveal that CuS nanorods are grown along the z-axis of chalcocite structure with Cu-7 and Cu-10 sites being the main building blocks. The hybridized absorption peak in the nanorods is shifted towards lower energies for smaller diameter of nanorods, which is attributed to surface reconstruction due to strong Cu-Cu interactions on the Cu-rich surface of the nanorods.
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| 10. |
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