70,080 research outputs found
Phosphorene nanoribbons
Edge-induced gap states in finite phosphorene layers are examined using
analytical models and density functional theory. The nature of such gap states
depends on the direction of the cut. Armchair nanoribbons are insulating,
whereas nanoribbons cut in the perpendicular direction (with zigzag and
cliff-type edges) are metallic, unless they undergo a reconstruction or
distortion with cell doubling, which opens a gap. All stable nanoribbons with
unsaturated edges have gap states that can be removed by hydrogen passivation.
Armchair nanoribbon edge states decay exponentially with the distance to the
edge and can be described by a nearly-free electron model
The Role of Fermions in Bubble Nucleation
We present a study of the role of fermions in the decay of metastable states
of a scalar field via bubble nucleation. We analyze both one and
three-dimensional systems by using a gradient expansion for the calculation of
the fermionic determinant. The results of the one-dimensional case are compared
to the exact results of previous work.Comment: 15 pages, revtex, 9 figure
X-ray powder diffraction of high-absorption materials at the XRD1 beamline off the best conditions: Application to (Gd,Nd)5Si4 compounds
Representative compounds of the new family of magnetic materials Gd5-xNdxSi4
were analyzed by X-ray diffraction at the XRD1 beamline at LNLS. To reduce
X-ray absorption, thin layers of the powder samples were mounted outside the
capillaries and measured in Debye-Scherrer geometry as usual. The X-ray
diffraction analyses and the magnetometry results indicate that the behavior of
the magnetic transition temperature as a function of Nd content may be directly
related to the average of the four smallest interatomic distances between
different rare earth sites of the majority phase of each compound. The quality
and consistency of the results show that the XRD1 beamline is able to perform
satisfactory X-ray diffraction experiments on high-absorption materials even
off the best conditions.Comment: 12 pages, 3 figures, 3 table
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