441 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
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
Electronic structure of the c(4 x 2) reconstructed Ge(001) surface
We investigate the electronic structure of the c(4 x 2) reconstructed Ge(001)
surface using band structure calculations based on density functional theory
and the generalized gradient approximation. In particular, we take into account
the details of surface reconstruction by means of well relaxed crystal
structures. The surface electronic states are identified and the local density
of states is compared to recent data from scanning tunneling spectroscopy. We
obtain almost perfect agreement between theory and experiment for both the
occupied and unoccupied states, which allows us to clarify the interpretation
of the experimental data.Comment: 4 pages, 3 figures, accepted by Chem. Phys. Let
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
Geometry Effects at Atomic-Size Aluminium Contacts
We present electronic structure calculations for aluminium nanocontacts.
Addressing the neck of the contact, we compare characteristic geometries to
investigate the effects of the local aluminium coordination on the electronic
states. We find that the Al 3pz states are very sensitive against modifications
of the orbital overlap, which has serious consequences for the transport
properties. Stretching of the contact shifts states towards the Fermi energy,
leaving the system instable against ferromagnetic ordering. By spacial
restriction, hybridization is locally suppressed at nanocontacts and the charge
neutrality is violated. We discuss the influence of mechanical stress by means
of quantitative results for the charge transfer.Comment: 10 pages, 4 figures, accepted by Chem. Phys. 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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