3,686 research outputs found
Fe adatoms along Bi lines on H/Si(001): Patterning atomic magnetic chains
The stability, electronic and magnetic properties of Fe atoms adsorbed on the
self-assembled Bi-dimer lines nanostructure on the H/Si(001) surface are
addressed by spin-density functional calculations. Our results show that Fe
adatoms are much more stable on sites closer to the Bi nanolines being able to
form one-dimensional atomic arrays. The most stable structure occurs on a
missing dimer line aside the Bi dimers, which corresponds to an array with
distances between Fe adatoms of about 8 Ang. In this array the irons are
coupled antiferromagnetically with spin magnetic moment of about 1.5 Bohr
magnetons per Fe atom, whereas the coupling exchange interactions is found to
be of 14.4 meV. We also estimate a large magnetic anisotropy energy for the Fe
adatom of about 3 meV/atom. In addition, the electronic band structure of the
Fe array at the most stable structure shows a magnetic half-metal behavior.Comment: 5 pages, 5 figures, accepted in AP
Theoretical Study of Carbon Clusters in Silicon Carbide Nanowires
Using first-principles methods we performed a theoretical study of carbon
clusters in silicon carbide nanowires. We examined small clusters with carbon
interstitials and antisites in hydrogen-passivated SiC nanowires growth along
the [100] and [111] directions. The formation energies of these clusters were
calculated as a function of the carbon concentration. We verified that the
energetic stability of the carbon defects in SiC nanowires depends strongly on
the composition of the nanowire surface: the energetically most favorable
configuration in carbon-coated [100] SiC nanowire is not expected to occur in
silicon-coated [100] SiC nanowire. The binding energies of some aggregates were
also obtained, and they indicate that the formation of carbon clusters in SiC
nanowires is energetically favored.Comment: 6 pages, 5 figures; 8 pages,
http://www.hindawi.com/journals/jnt/2011/203423
Hydrogenated grain boundaries in graphene
We have investigated by means of first principles calculations the structural
and electronic properties of hydrogenated graphene structures with distinct
grain boundary defects. Our total energy results reveal that the adsorption of
a single H is more stable at grain boundary defect. The electronic structure of
the grains boundaries upon hydrogen adsorption have been examined. Further
total energy calculations indicate that the adsorption of two H on two neighbor
carbons, forming a basic unit of graphane, is more stable at the defect region.
Therefore, we expect that these extended defects would work as a nucleation
region for the formation of a narrow graphane strip embedded in graphene
region
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