| 1. |
- Amft, Martin, et al.
(författare)
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Adsorption of Cu, Ag, and Au atoms on graphene including van der Waals interactions
- 2011
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Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 23:39
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Tidskriftsartikel (refereegranskat)abstract
- We performed a systematic density functional (DF) study of the adsorption of copper, silver, and gold adatoms on pristine graphene, especially accounting for van der Waals (vdW) interactions by the vdW-DF and PBE + D2 methods. In particular, we analyze the preferred adsorption site (among top, bridge, and hollow positions) together with the corresponding distortion of the graphene sheet and identify diffusion paths. Both vdW schemes show that the coinage metal atoms do bind to the graphene sheet and that in some cases the buckling of the graphene layer can be significant. Only the results for silver are qualitatively at variance with those obtained with the generalized gradient approximation, which gives no binding in this case. However in all three cases, we observe some quantitative differences between the vdW-DF and PBE + D2 methods. For instance the adsorption energies calculated with the PBE + D2 method are systematically higher than the ones obtained with vdW-DF. Moreover, the equilibrium distances computed with PBE + D2 are shorter than those calculated with the vdW-DF method.
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| 2. |
- Araujo, Carlos Moyses, et al.
(författare)
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Electronic and optical properties of MgH2: a first-principle GW investigation
- 2005
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 98:9, s. 096106-
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Tidskriftsartikel (refereegranskat)abstract
- The electronic structure of MgH2 is studied using the state of the art all-electron projector-augmented-wave GW approximation. Both the ground-state and the high-pressure transformations are considered in this investigation. We have found an indirect (direct) band-gap of 5.58 eV (6.52 eV) for α-MgH2, which has a good agreement with the experimental findings. For the γ- and β-phases, we have found indirect (direct) band-gap values of 5.24 eV (5.33 eV) and 3.90 eV (4.72 eV), respectively. The optical properties are investigated by means of the complex dielectric function, which is calculated within the framework of a full-potential linearized augmented plane wave method and corrected by scissor operators. All phases are found to be color neutral insulators.
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| 3. |
- Ben Romdhane, Ferdaous, et al.
(författare)
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Quasi-2D Cu2S Crystals on Graphene : In-situ Growth and ab-initio Calculations
- 2015
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Ingår i: Small. - : Wiley. - 1613-6810 .- 1613-6829. ; 11:11, s. 1253-1257
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Tidskriftsartikel (refereegranskat)abstract
- Two-dimensional crystals of beta-copper sulfide are synthesized in an in-situ electron microscopy experiment. Copper crystals are deposited on an amorphous carbon film containing sulfur. The carbon film graphitizes upon heating and electron irradiation and allows the reaction of Cu and S towards two-dimensional Cu2S crystals. These are energetically favourable and bonded via van der Waals interactions to the graphitic substrate.
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| 4. |
- Debbichi, Lamjed, et al.
(författare)
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Electronic structure of In3Se4 and In3Te4 monolayers from ab-initio calculations
- 2014
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Ingår i: Annalen der Physik. - : Wiley. - 0003-3804 .- 1521-3889. ; 526:9-10, s. 402-407
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Tidskriftsartikel (refereegranskat)abstract
- First principles calculations have been used to calculate the interlayer binding energy, the phonons frequencies, and the electronic structure of the In3X4 layered systems, with X = Se or Te. Using density functional theory corrected to take into account van der Waals interactions, the binding energy was found to be approximate to 41-44meV for In3Se4 and approximate to 53-58meV for In3Te4. Moreover, the absence of imaginary frequencies in the phonons bandstructures demonstrates the dynamical stability of the isolated layers. These facts suggest that isolated layers of In3Se4 and In3Te4 could be obtained by means of exfoliation from the bulk.
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| 5. |
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| 6. |
- Eriksson, Olle, et al.
(författare)
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Many-body projector orbitals for electronic structure theory of strongly correlated electrons
- 2005
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Ingår i: INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY. - : Wiley. - 0020-7608 .- 1097-461X. ; 105:2, s. 160-
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Tidskriftsartikel (refereegranskat)abstract
- We describe a technique to evaluate projector functions to be used, e.g., in self-interaction corrected versions of the Kohn-Sham equation (or in the LSDA+U method). The projector functions reproduce by construction the expectation values of spin and orbital moments (or any other property one is interested in) for the atomic many-body state. We therefore refer to these projector functions as many-body projector orbitals (MBPO). We describe how, once these projector states have been calculated, one can use them in any electronic structure method for a solid or molecule, to calculate ground-state properties of materials with strongly correlated states.
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| 7. |
- Lebegue, Sebastien, et al.
(författare)
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Ab initio study of the electronic properties and Fermi surface of the uranium dipnictides
- 2006
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Ingår i: PHYSICAL REVIEW B. - 1098-0121. ; 73:4, s. 045119-
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Tidskriftsartikel (refereegranskat)abstract
- The electronic structure of the uranium dipnictides UX2 (X=As, Sb, and Bi) is investigated by means of ab initio calculations based on density functional theory. The calculated Fermi surfaces are presented and compared to available experimental models obtained from de Haas-van Alphen experiments. In agreement with experiments they are found to have a significant two-dimensional character. Also, the change of the electronic properties through the series is discussed.
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| 8. |
- Lebegue, Sebastien, et al.
(författare)
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Electronic structure and spectroscopic properties of thulium monochalcogenides
- 2005
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Ingår i: PHYSICAL REVIEW B. - 1098-0121. ; 72:24, s. 245102-
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Tidskriftsartikel (refereegranskat)abstract
- The electronic structure of the thulium monochalcogenides TmS, TmSe, and TmTe is studied with several theoretical approaches. The total energy is evaluated with the self-interaction corrected local-spin density approximation, whereby the Tm ions are described with either twelve or thirteen localized f electrons with the remaining electrons forming bands. The comparisons of these two scenarios reveal the valency shift of the Tm ion through the series. The spectral functions of TmX compounds are calculated including multiplet effects, and they are compared to experimental x-ray photoemission spectra. The basic tool is the Hubbard-I approximation in which the embedding of an isolated f(n) ion in a solid is performed by modifying the crystal Hamiltonian as obtained from the local-density approximation with the atomic self-energy of the ion. The parameters of the model are obtained from the self-consistent band structure calculation. The agreement with experiment is excellent, reproducing all significant multiplet structures.
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| 9. |
- Lebègue, Sébastien, et al.
(författare)
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Molecular dynamics simulation and chemical bonding analysis of MgB2C2
- 2006
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Ingår i: Computational materials science. - : Elsevier BV. - 0927-0256 .- 1879-0801. ; 37:3, s. 220-225
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Tidskriftsartikel (refereegranskat)abstract
- The possible superconducting material MgB2C2 is studied by means of the Projector Augmented Plane wave method. The experimental lattice parameters and internal coordinates are reproduced with accuracy by means of a molecular dynamics calculation. A chemical bonding analysis is performed and it is found that the charge transfer from the Mg atoms to the BC network is not complete, meaning that a significant part of covalent bonding is present in this bond. In addition, a crystal orbital overlap population calculation reveals the degree of covalent bonding between atoms. This analysis is of particular importance and helps improve our general understanding of the superconductivity in these type of materials.
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| 10. |
- Lebègue, Sebastien, et al.
(författare)
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Multiplet effects in the electronic structure of heavy rare-earth metals
- 2006
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Ingår i: JOURNAL OF PHYSICS-CONDENSED MATTER. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 18, s. 6329-
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Tidskriftsartikel (refereegranskat)abstract
- The spectroscopic properties of elemental terbium, dysprosium, holmium, and erbium are investigated using first-principles calculations taking into account intra-atomic correlation effects. In order to describe the strongly localized f electrons together with the conduction bands, we have used the multiband Hubbard-I approximation to reproduce the multiplet features present in the experimental spectra. A comparison with available experimental data is made and the overall agreement is found to be good.
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