236 research outputs found
Self-assembled Pt nanowires on Ge(001): Relaxation effects
Absorption of Pt on the Ge(001) surface results in stable self-organized Pt
nanowires, extending over some hundred nanometers. Based on band structure
calculations within density functional theory and the generalized gradient
approximation, the structural relaxation of the Ge--Pt surface is investigated.
The surface reconstruction pattern obtained agrees well with findings from
scanning tunneling microscopy. In particular, strong Pt--Pt dimerization is
characteristical for the nanowires. The surface electronic structure is
significantly perturbed due to Ge--Pt interaction, which induces remarkable
shifts of Ge states towards the Fermi energy. As a consequence, the topmost Ge
layers are subject to a metal-insulator transition.Comment: 4 pages, 2 figures, final version accepted by Europhys. Lett., minor
modifications of the tex
Magnetic ordering in the striped nickelate La5/3Sr1/3NiO4: A band structure point of view
We report on a comprehensive study of the electronic and magnetic structure
of the striped nickelate La5/3Sr1/3NiO4. The investigation is carried out using
band structure calculations based on density functional theory. A magnetic
structure compatible with experiment is obtained from spin-polarized
calculations within the generalized gradient approximation (GGA), whereas
inclusion of a local Coulomb interaction in the LDA+U framework results in a
different ground state. The influence of the various interaction parameters is
discussed in detail.Comment: 5 pages, 4 figures, 2 tables, accepted by Europhys. Let
Electronic structure of the Au/benzene-1,4-dithiol/Au transport interface: Effects of chemical bonding
We present results of electronic structure calculations for well-relaxed
Au/benzene-1,4-dithiol/Au molecular contacts, based on density functional
theory and the generalized gradient approximation. Electronic states in the
vicinity of the Fermi energy are mainly of Au 5d and S 3p symmetry, whereas
contributions of C 2p states are very small. Hybridization between C 2p
orbitals within the benzene substructure is strongly suppressed due to S-C
bonding. In agreement with experimental findings, this corresponds to a
significantly reduced conductance of the molecular contact.Comment: 7 pages, 5 figures, accepted by Chemical Physics Letter
Magnetic ground state of coupled edge-sharing CuO_2 spin-chains
By means of density functional theory, we investigate the magnetic ground
state of edge-sharing CuO_2 spin-chains, as found in the
(La,Ca,Sr)_14Cu_24O_41system, for instance. Our data rely on spin-polarized
electronic structure calculations including onsite interaction (LDA+U) and an
effective model for the interchain coupling. Strong doping dependence of the
magnetic order is characteristic for edge-sharing CuO_2 spin-chains. We
determine the ground state magnetic structure as function of the spin-chain
filling and quantify the competing exchange interactions.Comment: 5 pages, 2 figures, 3 tables, accepted by Phys. Rev. Let
Confined Ge-Pt states in self-organized Pt nanowire arrays on Ge(001)
By means of band structure calculations within the density functional theory
and the generalized gradient approximation, we investigate the electronic
structure of self-organized Pt nanowires on the Ge(001) surface. In particular,
we deal with a novel one-dimensional surface state confined in the nanowire
array and clarify its origin. Due to large Pt contributions, the novel state is
rather a mixed Ge-Pt hybrid state than a confined Ge surface state. Moreover,
we compare our results to data from scanning tunneling microscopy.Comment: 3 pages, 3 figures, accepted by Eur. Phys. J.
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