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1.
  • Carbone, C., et al. (författare)
  • Correlated Electrons Step by Step : Itinerant-to-Localized Transition of Fe Impurities in Free-Electron Metal Hosts
  • 2010
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 104:11, s. 117601-
  • Tidskriftsartikel (refereegranskat)abstract
    • High-resolution photoemission spectroscopy and ab initio calculations have been employed to analyze the onset and progression of d-sp hybridization in Fe impurities deposited on alkali metal films. The interplay between delocalization, mediated by the free-electron environment, and Coulomb interaction among d electrons gives rise to complex electronic configurations. The multiplet structure of a single Fe atom evolves and gradually dissolves into a quasiparticle peak near the Fermi level with increasing host electron density. The effective multiorbital impurity problem within the exact diagonalization scheme describes the whole range of hybridizations.
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2.
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3.
  • Debbichi, L., et al. (författare)
  • Electronic structure of two-dimensional transition metal dichalcogenide bilayers from ab initio theory
  • 2014
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 89:20, s. 205311-
  • Tidskriftsartikel (refereegranskat)abstract
    • By means of first-principles GW calculations, we have studied the electronic structure properties of MX2 (M = Mo, W; X = S, Se, Te) bilayers, including hybrid structures of MX2 building blocks. The effect of spin-orbit coupling on the electronic structure and the effect of van der Waals interaction on the geometry were taken into account. All the homogeneous bilayers are identified as indirect band-gap materials, with an increase of the band gap when Mo is changed to W, and a decrease of the band gap when the atomic number of X is increased. The same behavior is also observed for hybrid bilayers with common chalcogen atoms, while bilayers with common metal atoms have a direct band gap. Finally, it is shown that due to their particular band alignment, some heterobilayers enable electron-hole separation, which is of interest for solar cell applications.
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4.
  • Debbichi, L., et al. (författare)
  • First-principles investigation of two-dimensional trichalcogenide and sesquichalcogenide monolayers
  • 2016
  • Ingår i: PHYSICAL REVIEW B. - 2469-9950. ; 93:24
  • Tidskriftsartikel (refereegranskat)abstract
    • We have used density functional theory to investigate the dynamical stability and the electronic structure of several new semiconducting two-dimensional single layers, with chemical compositions such as ABX(3) and A(2)X(3). The calculated interlayer binding energies and the absence of imaginary states in the phonon spectra indicate the possibility to isolate them in the form of a single layer. Also, the calculated band edges reveal that some of these two-dimensional materials are promising candidates for water-splitting applications.
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5.
  • Debbichi, L., et al. (författare)
  • Two-Dimensional Indium Selenides Compounds : An Ab Initio Study
  • 2015
  • Ingår i: The Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185. ; 6:15, s. 3098-3103
  • Tidskriftsartikel (refereegranskat)abstract
    • We use first-principle calculations to investigate the electronic structure of InSe and In2Se3. The interlayer binding energy is found to be in the same range as for other 2D systems, and the monolayers are found to be dynamically stable, which suggest the possibility to obtain them as isolated layers. The GW approximation including spin-orbit is used to obtain the bandgaps, which are in the range relevant for application in electronics. Also, it is shown that an electric field perpendicular to the layers can induce a semiconductor to metal transition in this family of compounds.
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6.
  • Di Marco, I., et al. (författare)
  • Electron correlations in Mn(x)Ga(1–x)As as seen by resonant electron spectroscopy and dynamical mean field theory
  • 2013
  • Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 4, s. 6-2645
  • Tidskriftsartikel (refereegranskat)abstract
    • After two decades since the discovery of ferromagnetism in manganese-doped gallium arsenide, its origin is still debated, and many doubts are related to the electronic structure. Here we report an experimental and theoretical study of the valence electron spectrum of manganese-doped gallium arsenide. The experimental data are obtained through the differences between off- and on-resonance photo emission data. The theoretical spectrum is calculated by means of a combination of density-functional theory in the local density approximation and dynamical mean field theory, using exact diagonalization as impurity solver. Theory is found to accurately reproduce measured data and illustrates the importance of correlation effects. Our results demonstrate that the manganese states extend over a broad range of energy, including the top of the valence band, and that no impurity band splits-off from the valence band edge, whereas the induced holes seem located primarily around the manganese impurity.
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7.
  • Di Marco, Igor, et al. (författare)
  • Electron correlations in MnxGa1-xAs as seen by resonant electron spectroscopy and dynamical mean field theory
  • 2013
  • Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723 .- 2041-1723. ; 4, s. 6-
  • Tidskriftsartikel (refereegranskat)abstract
    • After two decades since the discovery of ferromagnetism in manganese-doped gallium arsenide, its origin is still debated, and many doubts are related to the electronic structure. Here we report an experimental and theoretical study of the valence electron spectrum of manganese-doped gallium arsenide. The experimental data are obtained through the differences between off- and on-resonance photo emission data. The theoretical spectrum is calculated by means of a combination of density-functional theory in the local density approximation and dynamical mean field theory, using exact diagonalization as impurity solver. Theory is found to accurately reproduce measured data and illustrates the importance of correlation effects. Our results demonstrate that the manganese states extend over a broad range of energy, including the top of the valence band, and that no impurity band splits-off from the valence band edge, whereas the induced holes seem located primarily around the manganese impurity.
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8.
  • Fiori, G., et al. (författare)
  • Simulation of hydrogenated graphene field-effect transistors through a multiscale approach
  • 2010
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 82:15, s. 153404-
  • Tidskriftsartikel (refereegranskat)abstract
    • In this work, we present a performance analysis of field-effect transistors (FETs) based on recently fabricated 100% hydrogenated graphene (the so-called graphane) and theoretically predicted semihydrogenated graphene (i.e., graphone). The approach is based on accurate calculations of the energy bands by means of GW approximation, subsequently fitted with a three-nearest neighbor sp(3) tight-binding Hamiltonian, and finally used to compute ballistic transport in transistors based on functionalized graphene. Due to the large energy gap, the proposed devices have many of the advantages provided by one-dimensional graphene nanoribbon FETs, such as large I-on and I-on/I-off ratios, reduced band-to-band tunneling, without the corresponding disadvantages in terms of prohibitive lithography and patterning requirements for circuit integration.
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9.
  • Kaewmaraya, Thanayut, et al. (författare)
  • Theoretical investigation of xenon-hydrogen solids under pressure using ab initio DFT and GW calculations
  • 2011
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 84:9, s. 092101-
  • Tidskriftsartikel (refereegranskat)abstract
    • We have calculated crystal structures and electronic properties of Xe-H(2) compounds under high pressures using first-principles density functional theory calculations and ab-initio random structure searching. We present results for the equation of state, Xe-Xe separations, and the electronic charge transfer between the Xe and H atoms. Our results are broadly consistent with experimental results by M. Somayazulu et al. [Nature Chem. 2, 50 (2010)]. We have in addition calculated the metallization pressure within the GW approximation, finding it to be around 250 GPa, which is close to the maximum pressure reached in the experiment.
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10.
  • Kanchana, Venkatakrishnan, et al. (författare)
  • Density functional study of the electronic structure and lattice dynamics of SrCl2
  • 2010
  • Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 22:44, s. 445402-
  • Tidskriftsartikel (refereegranskat)abstract
    • A theoretical study of the structural, electronic, optical and lattice dynamical properties of SrCl2 in the cubic fluorite structure has been performed using first-principles calculations. The calculated ground state and elastic properties are in good agreement with the experiments. The calculated band gap is underestimated within the generalized gradient approximation for the exchange and correlation functional. GW calculations have been performed in order to improve the band gap and good agreement with the experiment is obtained. The phonon dispersion relations are discussed in detail in addition to the ground state and elastic properties. Also, the optical properties are computed with DFT corrected by the GW approximation.
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11.
  • Kim, D. Y., et al. (författare)
  • Crystal structure of the pressure-induced metallic phase of SiH4 from ab initio theory
  • 2008
  • Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 105:43, s. 16454-16459
  • Tidskriftsartikel (refereegranskat)abstract
    • Metallization of pure solid hydrogen is of great interest, not least because it could lead to high-temperature superconductivity, but it continues to be an elusive goal because of great experimental challenges. Hydrogen-rich materials, in particular, CH4, SiH4, and GeH4, provide an opportunity to study related phenomena at experimentally achievable pressures, and they too are expected to be high-temperature superconductors. Recently, the emergence of a metallic phase has been observed in silane for pressures just above 60 GPa. However, some uncertainty exists about the crystal structure of the discovered metallic phase. Here, we show by way of elimination, that a single structure that possesses all of the required characteristics of the experimentally observed metallic phase of silane from a pool of plausible candidates can be identified. Our density functional theory and GW calculations show that a structure with space group P4/nbm is metallic at pressures > 60 GPa. Based on phonon calculations, we furthermore demonstrate that the P4/nbm structure is dynamically stable at > 43 GPa and becomes the ground state at 97 GPa when zero-point energy contributions are considered. These findings could lead the way for further theoretical analysis of metallic phases of hydrogen-rich materials and stimulate experimental studies.
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12.
  • Kim, Duck Young, et al. (författare)
  • Structurally induced insulator-metal transition in solid oxygen : A quasiparticle investigation
  • 2008
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 77:9, s. 092104-
  • Tidskriftsartikel (refereegranskat)abstract
    • Structural phase transition of solid oxygen has been investigated by using ab initio calculations based on density functional theory. We found sudden jumps in structural parameters at the transition pressure, which confirm that the epsilon (epsilon) phase undergoes a first-order isostructural phase transformation to the zeta (zeta) phase. In particular, this happens without any molecular dissociation. Using the GW approximation to calculate the band-gap closure under high pressure, we show that the structural transition is accompanied by an insulator-metal transition, contrary to a standard density functional calculation which predicts a metallization at a much lower pressure in the epsilon phase.
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13.
  • Klintenberg, Mattias, et al. (författare)
  • Evolving properties of two-dimensional materials : from graphene to graphite
  • 2009
  • Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 21:33, s. 335502-
  • Tidskriftsartikel (refereegranskat)abstract
    • We have studied theoretically, using density functional theory, several material properties when going from one C layer in graphene to two and three graphene layers and on to graphite. The properties we have focused on are the elastic constants, electronic structure (energy bands and density of states), and the dielectric properties. For any of the properties we have investigated the modification due to an increase in the number of graphene layers is within a few per cent. Our results are in agreement with the analysis presented recently by Kopelevich and Esquinazi (unpublished).
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14.
  • Klintenberg, Mattias, et al. (författare)
  • Theoretical analysis of the chemical bonding and electronic structure of graphene interacting with Group IA and Group VIIA elements
  • 2010
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 81:8, s. 085433-
  • Tidskriftsartikel (refereegranskat)abstract
    • We propose a different class of materials, which can be viewed as graphene derivatives involving Group IA or Group VIIA elements, forming what we refer to as graphXene. We show that in several cases, large band gaps can be found to open up whereas in other cases, a semimetallic behavior is found. Formation energies indicate that under ambient conditions, sp(3) and mixed sp(2)/sp(3) systems will form. The results presented allow us to propose that by careful tuning of the relative concentration of the adsorbed atoms, it should be possible to tune the band gap of graphXene to take any value between 0 and 6.4 eV.
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15.
  • Lebegue, S, et al. (författare)
  • Accurate electronic band gap of pure and functionalized graphane from GW calculations
  • 2009
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 79:24, s. 245117-
  • Tidskriftsartikel (refereegranskat)abstract
    • Using the GW approximation, we study the electronic structure of the recently synthesized hydrogenated graphene, named graphane. For both conformations, the minimum band gap is found to be direct at the Gamma point, and it has a value of 5.4 eV in the stable chair conformation, where H atoms attach C atoms alternatively on opposite sides of the two-dimensional carbon network. In the metastable boat conformation the energy gap is 4.9 eV. Then, using a supercell approach, the electronic structure of graphane was modified by introducing either a hydroxyl group or an H vacancy. In this last case, an impurity state appears at about 2 eV above the valence-band maximum.
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16.
  • Lebegue, S, et al. (författare)
  • Electronic structure of two-dimensional crystals from ab initio theory
  • 2009
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 79:11, s. 115409-
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on ab initio calculations of the two-dimensional systems MoS2 and NbSe2, which recently were synthesized. We find that two-dimensional MoS2 is a semiconductor with a gap which is rather close to that of the three-dimensional analog, and that NbSe2 is a metal, which is similar to the three-dimensional analog of this compound. We further computed the electronic structure of the two-dimensional hexagonal (graphene-like) lattices of Si and Ge and compared them with the electronic structure of graphene. It is found that the properties related to the Dirac cone do not appear in the case of two-dimensional hexagonal germanium, which is metallic, contrary to two-dimensional hexagonal silicon, also known as silicene, which has an electronic structure very similar to the one of graphene, making them possibly equivalent.
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17.
  • Lebegue, S., et al. (författare)
  • Two-Dimensional Materials from Data Filtering and Ab Initio Calculations
  • 2013
  • Ingår i: Physical Review X. - 2160-3308. ; 3:3, s. 031002-
  • Tidskriftsartikel (refereegranskat)abstract
    • Progress in materials science depends on the ability to discover new materials and to obtain and understand their properties. This has recently become particularly apparent for compounds with reduced dimensionality, which often display unexpected physical and chemical properties, making them very attractive for applications in electronics, graphene being so far the most noteworthy example. Here, we report some previously unknown two-dimensional materials and their electronic structure by data mining among crystal structures listed in the International Crystallographic Structural Database, combined with density-functional-theory calculations. As a result, we propose to explore the synthesis of a large group of two-dimensional materials, with properties suggestive of applications in nanoscale devices, and anticipate further studies of electronic and magnetic phenomena in low-dimensional systems.
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18.
  • Oppeneer, Peter, et al. (författare)
  • Fermiology of PuCoGa5 and of related Pu-115 compounds
  • 2007
  • Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 444, s. 109-113
  • Tidskriftsartikel (refereegranskat)abstract
    • We report computational investigations of the electronic structures of the superconducting Pu-compounds PuCoGa5 as well as of the non-superconducting compounds PuFeGa5 and PuNiGa5. To capture the localization behavior of the Put 5f electrons, we apply two computational approaches, which are both rooted in the density-functional theory: the local spin-density approximation (LSDA) and the around mean field (AMF) LSDA + U approach. The latter is applicable to moderately localized 5f electrons while the former is applicable to delocalized 5f electrons. Our LSDA calculations show that the Fermi surfaces of the three Pu-115 compounds are sensitive to the amount of band filling, i.e., the number of electrons of the 3d element. Precisely at the electron filling corresponding to PuCoGa5 the Fermi surface has a particularly two-dimensional shape. AMF-LSDA+U calculations (with a Coulomb U of about 3 eV and exchange J of 0.6 eV) lead to a non-magnetic ground state for PuCoGa5, in which the 5f states are shifted to a higher binding energy, in better agreement with photoemission data. The Fermi surface of PuCoGa5 computed with the AMF-LSDA+U approach is nonetheless rather two-dimensional and similar to the LSDA Fermi surface. The AMFLSDA+U approach with a Coulomb U of approximate to 3 eV would thus predict an electronic structure for PuCoGa5 in accord with several experimental data.
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19.
  • Ramzan, M., et al. (författare)
  • Ab initio study of lithium and sodium iron fluorophosphate cathodes for rechargeable batteries
  • 2009
  • Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 94:15
  • Tidskriftsartikel (refereegranskat)abstract
    • The cathode materials Li2FePO4F and Na2FePO4F are studied by means of ab initio calculations. The generalized gradient approximation (GGA) and GGA+U are used to describe the crystal structures, and the electronic and magnetic properties of Li2FePO4F, Na2FePO4F, LiFePO4F, and NaFePO4F. Since only the lattice parameters are known for Li2FePO4F, our calculations predict the corresponding atomic positions, and reveal that the iron atom state (Fe-III or Fe-II) is changed during the reaction, which is of importance to understand the reactions taking place in rechargeable batteries. Finally, our calculated intercalation voltage with the GGA+U approximation is in good agreement with experimental value.
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20.
  • Ramzan, Muhammad, et al. (författare)
  • Correlation effects in the electronic and structural properties of Cr2AlC
  • 2011
  • Ingår i: PHYS STATUS SOLIDI-RAPID RE L. - : Wiley. - 1862-6254 .- 1862-6270. ; 5:3, s. 122-124
  • Tidskriftsartikel (refereegranskat)abstract
    • In this Letter, we present the electronic and structural properties calculated by first principles GGA and GGA+U calculations of Cr2AlC, a member of the MAX phases family of compounds. While GGA fails to obtain a correct description, the GGA+U method successfully reproduces the experimental equilibrium volume and bulk modulus values of Cr2AlC, and predict it to be a ferromagnet. Therefore, correlation effects are crucial for the correct description of Cr2AlC, provided that a suitable value of U is chosen.
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21.
  • Ramzan, Muhammad, et al. (författare)
  • Crystal and electronic structures of lithium fluorosulphate based materials for lithium-ion batteries
  • 2010
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 82:12, s. 125101-
  • Tidskriftsartikel (refereegranskat)abstract
    • By means of ab initio calculations, we study the electronic structure of LiFeSO4F, which has been shown recently [N. Recham et al., Nature Mater. 9, 68 (2010)] to be an excellent material as a cathode for lithium-ion batteries. We have obtained the crystal structure of FeSO4F, which was not completely determined experimentally, and compare the one of LiFeSO4F to available experimental values, resolving the issue about the position of the Li ion. Our calculated intercalation voltage (3.69 V) is found to be in excellent agreement with experiments. Finally, we have studied LiCoSO4F and LiNiSO4F, which are found to share a similar crystal structure with LiFeSO4F.
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22.
  • Ramzan, Muhammad, et al. (författare)
  • Electronic and mechanical properties of Cr2GeC with hybrid functional and correlation effects
  • 2012
  • Ingår i: Solid State Communications. - : Elsevier BV. - 0038-1098 .- 1879-2766. ; 152:13, s. 1147-1149
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a computational study of the MAX phase material Cr2GeC to obtain its crystal and electronic structure using density functional theory with various exchange-correlation functionals. While the GGA and GGA+U methods are giving a reasonable description of the lattice parameters, the hybrid functional (HSE06) is found to give too large values. Then, on the basis of our GGA+U calculations, the antiferromagnetic ordering is found to be the ground state. Furthermore, we study the charge distribution between the constituent elements of this compound and find that the simple ionic model fails to describe it due to the complex nature of this material. Finally, we conclude that the treatment of the correlated electrons is important for the correct description of this material.
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23.
  • Ramzan, Muhammad, et al. (författare)
  • Electronic structure and metalization of a silane-hydrogen system under high pressure investigated using density functional and GW calculations
  • 2010
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 81:23, s. 233103-
  • Tidskriftsartikel (refereegranskat)abstract
    • We have computed the electronic structure and the vibrational properties of the recently discovered hydrogen-rich compound silane-hydrogen [SiH4(H-2)(2)] from first principles, using density-functional theory. We have also studied the metallization under pressure of SiH4(H-2)(2) by the GW approximation, and obtained that the metallization occurs around 164 GPa, whereas the standard GGA calculations predict a metallization pressure around 145 GPa. Our results are compared with the recent experiment data of Strobel et al. [Phys. Rev. Lett. 103, 065701 (2009)] and Wang et al. [Proc. Natl. Acad. Sci. USA. 106, 14763 (2009)] and it is found that our calculated value of the metallization pressure is higher than the proposed experimental data. Some possible reasons for such a discrepancy are discussed in the text.
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24.
  • Ramzan, Muhammad, et al. (författare)
  • Hybrid exchange-correlation functional study of the structural, electronic, and mechanical properties of the MAX phases
  • 2011
  • Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 98:2, s. 021902-
  • Tidskriftsartikel (refereegranskat)abstract
    • In this letter, we report on our results obtained with the hybrid functional HSE06 on the structural, electronic, and mechanical properties of the MAX phases. As a sample, we choose Ti2AlN, Ti2AlC, V2AlC, Nb2AlC, Ta2AlC, V2GeC, Ti3SiC2, and Ti4AlN3, which cover all the known types of MAX phases. From our calculations, we have found that V2GeC has the magnetically ordered ground state. Our results are compared to available experimental data, and it is shown that the HSE06 functional can be used as a predictive tool to study the properties of this family of compounds.
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25.
  • Ramzan, Muhammad, et al. (författare)
  • Structural and energetic analysis of the hydrogen storage materials LiNH2BH3 and NaNH2BH3 from ab initio calculations
  • 2009
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 79:13
  • Tidskriftsartikel (refereegranskat)abstract
    • Ammonia borane (NH3BH3) possesses many appealing properties as a hydrogen storage material; however, the release of trace amounts of borazine during the desorption process is troublesome. Recently, it was found that substitution of one of the H atoms in the NH3 group by Li or Na could significantly improve the hydrogen desorption properties. The resulting lithium amidoborane (LiNH2BH3) and sodium amidoborane (NaNH2BH3) compounds have been studied by us using density-functional theory. Specifically, we have succeeded in determining the detailed crystal structures of LiNH2BH3 and NaNH2BH3, including the atomic positions in their respective unit cells. Calculated hydrogen removal energies of the hydrogen release reactions are found to be in good agreement with the experimental trend.
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26.
  • Ramzan, M., et al. (författare)
  • Structural, magnetic, and energetic properties of Na2FePO4F, Li2FePO4F, NaFePO4F, and LiFePO4F from ab initio calculations
  • 2009
  • Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 106:4
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper, we report on Na2FePO4F and Li2FePO4F, which are materials that are used as cathodes in batteries, using density functional theory with the LDA, LDA+U, GGA, or GGA+U approximations. Specifically, we study their crystal structure, electronic structure, and magnetic properties and provide similar information about the intermediate compounds LiFePO4F and NaFePO4F. Finally, the intercalation voltages of the corresponding batteries are calculated using various exchange-correlation approximations and conclusions are drawn about which one is the most suitable to use for the study of this class of materials.
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27.
  • Ramzan, Muhammad, et al. (författare)
  • Transition metal doped MgH2 : A material to potentially combine fuel-cell and battery technologies
  • 2010
  • Ingår i: International journal of hydrogen energy. - : Elsevier BV. - 0360-3199 .- 1879-3487. ; 35:19, s. 10373-10376
  • Tidskriftsartikel (refereegranskat)abstract
    • MgH2 is studied as a negative electrode material for rechargeable batteries on the basis of density functional theory calculations. We calculate the average voltage of the corresponding Li-ion battery, which is in good agreement with the experimental value, and we predict the average voltage for the Na-ion battery. Then, molecular dynamics simulations are used to study the diffusive properties of lithium in MgH2 clusters. In particular, we dope MgH2 with transition metals (Fe, Ni, Ti, and V), and analyze the effect on the diffusion of lithium, which is shown to be essentially unaffected. Therefore, we propose that transition metal doped MgH2 is a material that can be used efficiently in both batteries and fuel-cell technologies.
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28.
  • Rusz, Jan, et al. (författare)
  • Probing the electronic structure of pure and doped CeMIn5 (M=Co,Rh,Ir) crystals with nuclear quadrupolar resonance
  • 2008
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 77:24, s. 245124-
  • Tidskriftsartikel (refereegranskat)abstract
    • We report calculations of the electric-field gradients (EFGs) in pure and doped CeMIn5 (M=Co, Rh, and Ir) compounds and compare with experiment. The degree to which the Ce 4f electron is localized is treated within various models: the local-density approximation, generalized gradient approximation (GGA), GGA+U, and 4f-core approaches. We find that there is a correlation between the observed EFG and whether the 4f electron participates in the band formation or not. We also find that the EFG evolves linearly with Sn doping in CeRhIn5, suggesting the electronic structure is modified by doping. In contrast, the observed EFG in CeCoIn5 doped with Cd changes little with doping. These results indicate that nuclear quadrupolar resonance is a sensitive probe of electronic structure.
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29.
  • Scheicher, Ralph H., et al. (författare)
  • Cubic metallic phase of aluminum hydride showing improved hydrogen desorption
  • 2008
  • Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 92:20
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on our results calculated from density functional theory and GW of the dehydrogenation properties in a cubic phase of AlH3. The metallic nature of the electronic structure entails a more favorable hydrogen removal energy which is lowered by 75% compared to the insulating hexagonal phase. This remarkable reduction in the Al-H bond strength bears important consequences for feasible applications of AlH3 as an on-board hydrogen storage material for mobile applications. We suggest that the cubic phase could be prepared and stabilized experimentally at ambient pressure by off-board quenching.
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30.
  • Silvearv, Fredrik, 1973-, et al. (författare)
  • An ab-initio study of (Mn,Al) doped ZnO including strong correlation effects
  • 2012
  • Ingår i: Physica. E, Low-Dimensional systems and nanostructures. - : Elsevier BV. - 1386-9477 .- 1873-1759. ; 44:6, s. 1095-1097
  • Tidskriftsartikel (refereegranskat)abstract
    • (Mn,Al)-codoped ZnO has been investigated by means of first-principles calculations using density-functional theory within the generalized-gradient approximation plus on-site Coulomb interaction (GGA + U) to take into the strong correlations on the Mn site. It is found that for several Al-Mn distances, the system shows always an antiferromagnetic behavior. This is explained by the fact that even with the correct electronic structure described with the GGA + U scheme, the extra electron brought by Al is localized in the host conduction band, and therefore does not modify the occupation of the Mn atoms, suggesting that the antiferromagnetic interaction is still dominant. 
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31.
  • Thunström, P, et al. (författare)
  • Multiplet effects in the electronic structure of intermediate-valence compounds
  • 2009
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 79:16, s. 165104-
  • Tidskriftsartikel (refereegranskat)abstract
    • We present an implementation of the Hubbard-I approximation based on the exact solution of the atomic many-body problem incorporated in a full-potential linear muffin-tin orbital method of density-functional theory. Comparison between calculated and measured x-ray photoemission spectra reveal a good agreement for intermediate valence systems in open crystal structures such as YbInCu4, SmB6, and YbB12. Spectral features of the unoccupied states of SmB6 are predicted.
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