| 1. |
- Karis, O, et al.
(författare)
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Probing surface states of Cu/Ni thin films using x-ray absorption spectroscopy
- 2001
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 63:11
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Tidskriftsartikel (refereegranskat)abstract
- Surface and interface properties of Cu thin films (1–4 monolayers) deposited on Ni(100) have been extracted by means of x-ray absorption spectroscopy and analyzed in combination with ab initio density-functional calculations. An unoccupied Cu surface state is identified in an x-ray absorption spectra and studied as a function of film thickness. Experimental data is supported by calculations of the layer-resolved density of states and the results from this combined theoretical-experimental effort show that the surface state is almost entirely located on the atomic layer closest to the vacuum. Our results also indicate strong hybridization between unoccupied states at the Cu/Ni interface boundary.
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| 2. |
- Mattesini, M., et al.
(författare)
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Electronic structure and optical properties of solid C-60
- 2009
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Ingår i: Physica. B, Condensed matter. - : Elsevier BV. - 0921-4526 .- 1873-2135. ; 404:12-13, s. 1776-1780
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Tidskriftsartikel (refereegranskat)abstract
- The electronic structure and the optical properties of face-centered-cubic C-60 have been investigated by using an all-electron full-potential method. Our ab initio results show that the imaginary dielectric function for high-energy values looks very similar to that of graphite, revealing close electronic structure similarities between the two systems. We have also identified the origin of different peaks in the dielectric function of fullerene by means of the calculated electronic density of states. The computed optical spectrum compares fairly well with the available experimental data for the Vis-UV absorption spectrum of solid C-60.
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| 3. |
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| 4. |
- Hugosson, Håkan Wilhelm, et al.
(författare)
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Phase stabilities and structural relaxations in substoichiometric TiC1-x
- 2001
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 6316:16, s. 165116-
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Tidskriftsartikel (refereegranskat)abstract
- First-principles calculations have been used to study the effect of vacancies and relaxation around the vacancy sites in substoichiometric TiC1-x. The effect of relaxation on phase stabilities, equilibrium volumes. and electronic structure of the substoichiometric phases was studied using a combined approach of pseudopotential plane wave and full-potential linear muffin-tin orbital methods. A relaxation away from the vacancies was found for the titanium atoms, the magnitude of which increased with vacancy concentration and the inclusion of nearest-neighbor carbon atom relaxation. The inclusion of local relaxations was found to correctly predict the off-stoichiometric equilibrium composition of titanium carbide. The anomalous volume behavior of TiC at small vacancy concentration is explained as an effect of the local relaxation of the atoms surrounding the vacancy sites, but we do not find that the lattice parameter of any of the studied stoichiometries is larger than that of ideal stoichiometric TiC.
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| 5. |
- Hugosson, Håkan Wilhelm, et al.
(författare)
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Phase stability diagrams of transition metal carbides, a theoretical study
- 2001
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Ingår i: CHEMICAL PHYSICS LETTERS. - 0009-2614 .- 1873-4448. ; 333:6, s. 444-450
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Tidskriftsartikel (refereegranskat)abstract
- The experimental phase diagrams at T=0 of the refractory compounds ZrC, NbC and MoC have been reproduced with great accuracy from first principles theory. The energy of formation for these compounds has been calculated for several phases and stoichiometries in order to understand, for example, the differences and changes in homogeneity ranges found in these systems. This determination of relative phase stabilities for a wide range of concentrations is necessary for first principles determination of phase diagrams for these compounds with complex bonding and structural properties as well as technological importance.
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| 6. |
- Hugosson, Håkan Wilhelm, et al.
(författare)
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Restricting dislocation movement in transition metal carbides by phase stability tuning
- 2001
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 293:5539, s. 2434-2437
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Tidskriftsartikel (refereegranskat)abstract
- A mechanism to enhance hardness in multilayer coatings is proposed. Using the technologically important hard transition metal carbides as prototypes, although the principle is transferable also to other systems, we demonstrate, from first-principles calculations, that by suitable alloying the energy difference between several competing structures in the transition meta[ carbides is small or tunable. This creates multiphase/polytypic compounds with a random or controllable layer stacking sequence, systems in which the propagation of dislocations can be strongly suppressed by a large number of interfaces between structures with different glide systems, accordingly allowing the possibility of a greatly enhanced hardness. With modern thin-film technologies, it should therefore be possible to deposit such materials that will express multilayer characteristics with only minor changes in the chemical constitution of the material, which is in contrast to conventional superlattices.
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| 7. |
- Lundin, U, et al.
(författare)
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Correlation mechanism of f-electron delocalization
- 2000
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 62:24, s. 16370-16377
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Tidskriftsartikel (refereegranskat)abstract
- The mechanism off-electron delocalization is investigated within the multiorbital Anderson lattice model by means of diagrammatic perturbation theory from the atomic limit. The derived equations couple the intraatomic transition energies, their spectral weights, and the population numbers of the many-electron states. A self-consistent solution for praseodymium metal shows that the delocalization can be caused by external pressure via a resonant mixing off and conduction electrons in the vicinity of the the Fermi surface. We also find the following. (1) An increase of mixing leads to a decrease of the physical values of the Hubbard interactions U*, the reduction, however, is small. (2) The initial Hubbard U is split by renormalization into a set of different physical values of U*(i,j). (3) The gain in cohesive energy together with the f-sum rule cause a transfer of spectral weight, which is decisive for the delocalization off electrons. (4) The correlated fermionic quasiparticles have their bandwidth slightly reduced compared to those obtained using the Kohn-Sham equation.
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| 8. |
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| 9. |
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| 10. |
- Ahuja, R., et al.
(författare)
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Electronic structure of Ti3SiC2
- 2000
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 76:16, s. 2226-2228
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Tidskriftsartikel (refereegranskat)
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