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- Bhandary, Sumanta, 1985-, et al.
(författare)
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Controlling electronic structure and transport properties of zigzag graphene nanoribbons by mono- and difluorinated edge functionalization
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- In this work, we report a detailed study of the electronic structure and transport properties of mono- and di-fluorinated edges of zigzag graphene nanoribbons (ZGNR) using density functional theory (DFT). The calculated formation energies at 0K indicate that the stability of the nanoribbons increases with the increase in the concentration of di-fluorinated edge C atoms along with an interesting variation of the energy gaps between 0.0 to 0.66 eV depending on the concentration. This gives a possibility of tuning the band gaps by controlling the concentration of F for terminating the edges of the nanoribbons. The DFT results have been reproduced by single band tight binding as well as density functional tight binding methods. Using non-equilibrium Green functional method, we have calculated the transmission coecients of several mono and di-fluorinated ZGNR as a function of unit cell size and degree of homogeneous disorder caused by the random placement of mono and di-fuorinated C atoms at the edges.
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- Bhandary, Sumanta, 1985-, et al.
(författare)
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Correlated electron behavior of metalorganic molecules: insights from density functional theory and exact diagonalization studies.
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The proper description of electronic structure of correlated orbitals in the metal centers of functional metalorganics is a challenging problem. In this letter, we apply density functional theory and exact diagonalization method in a many body approach to study the ground state electronic conguration of iron porphyrin (FeP) molecule. Our study reveals that FeP is a potential candidate for realizing a spin crossover due to a subtle balance of crystal elds and hybridization of the Fe d-orbitals and ligand N p-states. Moreover, the mechanism of switching between two close lying electronic congurations of Fe-d orbitals is revealed. This hybrid method can generally be applied to properly describe the electronic and related low energy physics of the whole class of correlated metal centered organometallic molecules.
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- Björkman, Torbjörn, 1977-, et al.
(författare)
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Theoretical investigation of the volume collapse of CeOFeAs under pressure
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We conduct a density functional theory study of the high TC superconductor CeOFeAs using the self-interaction corrected local density approximation (LDA-SIC). We find that under compression the compound undergoes a transition from localized to delocalized Ce 4f -states at a pressure close to the experimentally observed point of vanishing superconductivity. This suggests that the observed abruptly vanishing superconductivity under pressure may have its origin in a Mott transition of the 4f electrons of the CeO layer.
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- Bondarenko, Nina, et al.
(författare)
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Static and dynamical properties of spin-polarons in La-doped CaMnO3
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The static and dynamic properties of spin-polarons in La-doped CaMnO3 are explored theoretically,by means of an eective low energy Hamiltonian. All parameters from the Hamiltoniainare evaluated from rst principles theory, without adjustable parameters. We compare dierentgeometries, like spin-polarons in bulk, surface and as single two-dimensional layers. The low energyHamiltonian is used to investigate the temperature stability of the spin-polaron, as well as theresponse to an external applied electric eld. Technically this involves atomistic spin-dynamics simulationsin combination with kinetic Monte Carlo simulations. Where a comparison can be made,our simulations exhibit an excellent agreement with available experimental data and previous theory.Remarkably, we nd that excellent control of the mobility of spin-polarons in this material canbe achieved, and that the critical parameters deciding this is the temperature and strength of theapplied electrical eld. We outline dierent technological implications of our ndings.
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- Cardias, Ramon, 1990-, et al.
(författare)
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First-principles Dzyaloshinskii-Moryia interaction in a non-collinear framework
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Including dierent terms in the spin-Hamiltonian, we have derived an expression for theDzyaloshinskii-Moryia vector interaction (DMI) where all the three components of the vector canbe calculated independently of the magnetic conguration. Here, we have chosen the Cr triangulartrimer on Au(111) and Mn triangular trimes on Ag(111) and Au(111) surfaces to study the implementationof the derived DMI into the RS-LMTO-ASA method. Our results have shown thatthe DMI value (module and direction) is drastically dierent for collinear and non-collinear states.Based on relation between the spin and charge currents owing in the system and the non-collinearmagnetic conguration of the triangular trimer, we argued that the drastic change between the DMIcalculated considering a collinear and a non-collinear magnetic conguration can be explained bythe mechanism behind the spin and charge currents owing through the atoms when the spins arealigned in a non-collinear fashion.
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- Carvalho de Melo Rodrigues, Debora, et al.
(författare)
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Prediction of a Larger Local Magnetic Anisotropy in Permalloy
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- By means of relativistic, first principles calculations, we investigate the microscopic origin of the vanishingly low magnetic anisotropy of Permalloy. Analyzing the local magnetic anisotropy of these alloys, we find that it can be several orders of magnitude larger than that of the bulk sample, and at least one order of magnitude larger than that of Fe or Ni. We discuss these results in terms of local symmetries of the alloy, and point out that an analysis based on perturbation theory has the spin-orbit coupling entering as a second-order term, as opposed to the naively expected fourth order contribution. The relevance for these findings in experiments, e.g. using pump-probe investigations, is discussed, as well as the implications for building effective spin-Hamiltonians of Permalloy.
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