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Träfflista för sökning "WAKA:ref ;pers:(Eriksson Olle);pers:(Rusz Jan)"

Sökning: WAKA:ref > Eriksson Olle > Rusz Jan

  • Resultat 1-10 av 26
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1.
  • Bhowmick, Somnath, et al. (författare)
  • X-ray absorption spectra : Graphene, h-BN, and their alloy
  • 2013
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121. ; 87:15, s. 155108
  • Tidskriftsartikel (refereegranskat)abstract
    • Using first-principles density functional theory calculations, in conjunction with the Mahan-Nozieres-de Dominicis theory, we calculate the x-ray absorption spectra of the alloys of graphene and monolayer hexagonal boron nitride on a Ni (111) substrate. The chemical neighborhood of the constituent atoms (B, C, and N) inside the alloy differs from that of the parent phases. In a systematic way, we capture the change in the K-edge spectral shape, depending on the chemical neighborhood of B, C, and N. Our work also reiterates the importance of the dynamical core-hole screening for a proper description of the x-ray absorption process in sp(2)-bonded layered materials.
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2.
  • Bidermane, Ieva, et al. (författare)
  • Experimental and theoretical study of electronic structure of lutetium bi-phthalocyanine
  • 2013
  • Ingår i: Journal of Chemical Physics. - American Institute of Physics (AIP). - 0021-9606. ; 138:23, s. 234701
  • Tidskriftsartikel (refereegranskat)abstract
    • Using Near Edge X-Ray Absorption Fine Structure (NEXAFS) Spectroscopy, the thickness dependent formation of Lutetium Phthalocyanine (LuPc2) films on a stepped passivated Si(100)2x1 reconstructed surface was studied. Density functional theory (DFT) calculations were employed to gain detailed insights into the electronic structure. Photoelectron spectroscopy measurements have not revealed any noticeable interaction of LuPc2 with the H-passivated Si surface. The presented study can be considered to give a comprehensive description of the LuPc2 molecular electronic structure. The DFT calculations reveal the interaction of the two molecular rings with each other and with the metallic center forming new kinds of orbitals in between the phthalocyanine rings, which allows to better understand the experimentally obtained NEXAFS results.
3.
  • Delczeg-Czirjak, Erna K., et al. (författare)
  • Stabilization of the tetragonal distortion of Fe chi Co1-chi alloys by C impurities : A potential new permanent magnet
  • 2014
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121. ; 89:14, s. 144403
  • Tidskriftsartikel (refereegranskat)abstract
    • We have analyzed by density functional theory calculations the structural and magnetic properties of Fe-Co alloys doped by carbon. In analogy with the formation of martensite in steels we predict that such a structure also forms for Fe-Co alloys in a wide range of concentrations. These alloys are predicted to have a stable tetragonal distortion, which in turn leads to an enhanced magnetocrystalline anisotropy energy of up to 0.75 MJ/m(3) and a saturated magnetization field of 1.9 T.
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4.
  • Kocevski, Vancho, 1984-, et al. (författare)
  • Band alignment switching and the interaction between neighbouring silicon nanocrystals embedded in a SiC matrix
  • 2015
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121. ; 91, s. 165429-165435
  • Tidskriftsartikel (refereegranskat)abstract
    • We present results from density functional theory of the electronic properties of silicon nanocrystals (Si NCs) embedded in a silicon carbide (SiC) matrix, considering different combinations of various NCs and host matrix sizes. We show that the NC and the host matrix form a type-II band alignment, with the states at the top of the valence band being in the Si NC and the states at the bottom of the conduction band in the host matrix. Moreover, this band alignment can be interchanged with introducing oxygen at the interface. We demonstrate that the charge densities of some valence band states can overlap with the charge densities of the neighbouring NCs. We also demonstrate that this leakage of states is significant when the distance between the neighbouring NCs is less than ~1.6 nm.
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5.
  • Kocevski, Vancho, 1984-, et al. (författare)
  • First-principles study of the influence of different interfaces and core types on the properties of CdSe/CdS core-shell nanocrystals
  • ????
  • Ingår i: Scientific Reports. - 2045-2322.
  • Tidskriftsartikel (refereegranskat)abstract
    • With the expanding field of nanoengineering and the production of nanocrystals (NCs) with higher quality and tunable size, having reliable theoretical calculations to complement the experimental results is very important. Here we present such a study of CdSe/CdS core-shell NCs using density functional theory, where we focus on dependence of the properties of these NCs on core types and interfaces between the core and the shell, as well as on the core/shell ratio. We show that the density of states and the absorption indices depend rather weakly on the type of interface and core type. We demonstrate that the HOMO wavefunction is mainly localised in the core of the nanocrystal, depending primarily on the core/shell ratio. On the other hand the LUMO wavefunction spreads more into the shell of the nanocrystal, where its confinement in the core is almost the same in each of the studied structural models. Furthermore, we show that the radiative lifetimes decrease with increasing core sizes due to changes in the dipolar overlap integral of the HOMO and LUMO wavefunctions. In addition, the electron-hole Coulomb interaction energies follow a similar pattern as the localisation of the wavefunctions, with the smaller NCs having higher Coulomb interaction energies.
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6.
  • Kocevski, Vancho, 1984-, et al. (författare)
  • Size dependence of the stability, electronic structure, and optical properties of silicon nanocrystals with various surface impurities
  • 2015
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121. ; 91:12
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a comprehensive, ground-state density functional theory study of the size dependence of the optical and electronic properties and the stability of spherical silicon nanocrystals (NCs) with different impurities on the surface. We vary the size of the NCs from 1.0 to 3.5 nm, considering single-bonded (CH3, F, Cl, OH) and double-bonded (O, S) impurities and bridged oxygen. We show that the density of states (DOS) and absorption indices of the NCs with single-bonded impurities are very similar to each other and the fully hydrogenated NCs, except for the 1.0-nm NCs, where a slight difference is present. In the case of the NCs with double-bonded impurities, the DOS and absorption indices exhibit a significant difference, compared to the fully hydrogenated NCs, for sizes up to 2.5 nm. We argue that this difference arises from the difference in the contribution from the impurity to the states around the gap, which can considerably change the character of the states. We demonstrate that the double-bonded impurities contribute significantly to the states around the gap, compared to the single-bonded impurities, causing changes in the symmetry of these states. This observation was further supported by analyzing the changes of the Fourier transform of the charge densities of the highest occupied and lowest unoccupied eigenstate. We also show that the formation energies of NCs with bridged oxygen and fluorine are the lowest, regardless of the size. Furthermore, we show that high hydrogen concentration can be used to suppress the addition of oxygen and fluorine on the surface of the Si NCs.
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7.
  • Kocevski, Vancho, et al. (författare)
  • Transition between direct and indirect band gap in silicon nanocrystals
  • 2013
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121. ; 87:24, s. 245401
  • Tidskriftsartikel (refereegranskat)abstract
    • Using ground-state density functional theory we study the transition from indirect to direct band gap in hydrogen-terminated silicon nanocrystals (NCs) as a function of decreasing diameter. The studied range, from 1.0 to 4.6 nm diameter of nanocrystals, with spherical and Wulff-shape NCs, covers the transition from nano-to bulk regime. A change in the symmetry of the lowest unoccupied state as a function of decreasing NC diameter is observed, gradually increasing the oscillator strength of transitions from the highest occupied to the lowest unoccupied state. Real space and Fourier space characteristics of highest occupied and lowest unoccupied states are explored in detail and linked to a smooth transition from nano-to bulk regime.
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  • Resultat 1-10 av 26
  • [1]23Nästa
 
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