714 research outputs found
Effect of Ultrahigh Stiffness of Defective Graphene from Atomistic Point of View
Well-known effect of mechanical stiffness degradation under the influence of
point defects in macroscopic solids can be controversially reversed in the case
of low-dimensional materials. Using atomistic simulation, we showed here that a
single-layered graphene film can be sufficiently stiffened by monovacancy
defects at a tiny concentration. Our results correspond well with recent
experimental data and suggest that the effect of mechanical stiffness
augmentation is mainly originated from specific bonds distribution in the
surrounded monovacancy defects regions. We showed that such unusual mechanical
response is the feature of presence of specifically monovacancies, whereas
other types of point defects such as divacancy, 555-777 and Stone-Wales
defects, lead to the ordinary degradation of the graphene mechanical stiffness.Comment: 9 pages, 3 figure
Multiterminal Nanowire Junctions of Silicon: A Theoretical Prediction of Atomic Structure and Electronic Properties
Using empirical scheme, atomic structure of a new exotic class of silicon
nanoclusters was elaborated upon the central icosahedral core (Si-IC) and
pentagonal petals (Si-PP) growing from Si-IC vertexes. It was shown that
Si-IC/Si-PP interface formation is energetically preferable. Some experimental
observations of silicon nanostructures can be explained by presence of the
proposed objects. The Extended Huckel Theory electronic structure calculations
demonstrate an ability of the proposed objects to act as nanoscale tunnel
junctions.Comment: 13 pages, 3 figures, 1 tabl
The theoretical DFT study of electronic structure of thin Si/SiO2 quantum nanodots and nanowires
The atomic and electronic structure of a set of proposed thin (1.6 nm in
diameter) silicon/silica quantum nanodots and nanowires with narrow interface,
as well as parent metastable silicon structures (1.2 nm in diameter), was
studied in cluster and PBC approaches using B3LYP/6-31G* and PW PP LDA
approximations. The total density of states (TDOS) of the smallest
quasispherical silicon quantum dot (Si85) corresponds well to the TDOS of the
bulk silicon. The elongated silicon nanodots and 1D nanowires demonstrate the
metallic nature of the electronic structure. The surface oxidized layer opens
the bandgap in the TDOS of the Si/SiO2 species. The top of the valence band and
the bottom of conductivity band of the particles are formed by the silicon core
derived states. The energy width of the bandgap is determined by the length of
the Si/SiO2 clusters and demonstrates inverse dependence upon the size of the
nanostructures. The theoretical data describes the size confinement effect in
photoluminescence spectra of the silica embedded nanocrystalline silicon with
high accuracy.Comment: 22 pages, 5 figures, 1 tabl
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