14 research outputs found
Resistive and rectifying effects of pulling gold atoms at thiol-gold nano-contacts
We investigate, by means of first-principles calculations, structural and
transport properties of junctions made of symmetric dithiolated molecules
placed between Au electrodes. As the electrodes are pulled apart, we find that
it becomes energetically favorable that Au atoms migrate to positions between
the electrode surface and thiol terminations, with junction structures
alternating between symmetric and asymmetric. As a result, the calculated
\emph{IV} curves alternate between rectifying and non-rectifying behaviors as
the electrodes are pulled apart, which is consistent with recent experimental
results
Bistability, softening, and quenching of magnetic moments in Ni-filled carbon nanotubes
The authors apply first-principles calculations to investigate the interplay
between structural, electronic, and magnetic properties of nanostructures
composed of narrow nanotubes filled with metallic nanowires. The focus is on
the structural and magnetic responses of Ni-filled nanotubes upon radial
compression. Interestingly, metastable flattened structures are identified, in
which radially deformed nanotubes are stabilized by the interactions with the
encapsulated wire. Moreover, our results indicate a quenching of the magnetic
moment of the wire upon compression, as a result of the transfer of charge from
the to the orbitals of the atoms in the wire.Comment: 4 pages, 4 figure
Non-hexagonal-ring defects and structures induced by strain in graphene and in functionalized graphene
We perform {\textit ab initio} calculations for the strain-induced formation
of non-hexagonal-ring defects in graphene, graphane (planar CH), and graphenol
(planar COH). We find that the simplest of such topological defects, the
Stone-Wales defect, acts as a seed for strain-induced dissociation and
multiplication of topological defects. Through the application of inhomogeneous
deformations to graphene, graphane and graphenol with initially small
concentrations of pentagonal and heptagonal rings, we obtain several novel
stable structures that possess, at the same time, large concentrations of
non-hexagonal rings (from fourfold to elevenfold) and small formation energies
Water diffusion in carbon nanotubes for rigid and flexible models
We compared the diffusion of water confined in armchair and zigzag carbon
nanotubes for rigid and flexible water models. Using one rigid model,
TIP4P/2005, and two flexible models, SPC/Fw and SPC/FH, we found that the
number of the number of hydrogen bonds that water forms depends on the
structure of the nanotube, directly affecting the diffusion of water. The
simulation results reveal that due to the hydrophobic nature of carbon
nanotubes and the degrees of freedom imposed by the water force fields, water
molecules tend to avoid the surface of the carbon nanotube. This junction of
variables plays a central role in the diffusion of water, mainly in narrow
and/or deformed nanotubes, governing the mobility of confined water in a
non-trivial way, where the greater the degree of freedom of the water force
field, the smaller it will be mobility in confinement, as we limit the
competition between area/volume, and it no longer plays the unique role in
changing water diffusivity.Comment: 28 pages, 6 figure
Phyllosilicates as earth-abundant layered materials for electronics and optoelectronics: Prospects and challenges in their ultrathin limit
Phyllosilicate minerals are an emerging class of naturally occurring layered
insulators with large bandgap energy that have gained attention from the
scientific community. This class of lamellar materials has been recently
explored at the ultrathin two-dimensional level due to their specific
mechanical, electrical, magnetic, and optoelectronic properties, which are
crucial for engineering novel devices (including heterostructures). Due to
these properties, phyllosilicates minerals can be considered promising low-cost
nanomaterials for future applications. In this Perspective article, we will
present relevant features of these materials for their use in potential
2D-based electronic and optoelectronic applications, also discussing some of
the major challenges in working with them.Comment: 29 pages, 4 figure