77 research outputs found
Strain engineering and photocatalytic application of single-layer ReS
We present a theoretical study on the electronic, dynamical, and
photocatalytic properties of single-layer ReS under uniaxial and shear
strains. The single-layer ReS shows strong anisotropic responses to
straining. It remains dynamically stable for a wide range of -axial strain,
but becomes unstable for 2\% -axial compressive strain. The single-layer
ReS is calculated to be an indirect bandgap semiconductor, and there is an
indirectdirect bandgap transition under 15\% -axial tensile straining.
The single-layer ReS is predicted incapable of catalyzing the water
oxidation reaction. However, 15\% -axial tensile strain can enable the
single-layer ReS for overall photocatalytic water splitting. Besides, the
single-layer ReS can also catalyze the overall water splitting and be most
efficient under acidic water solutions with pH=3.8
Impurity effects on the grain boundary cohesion in copper
Segregated impurities at grain boundaries can dramatically change the
mechanical behavior of metals, while the mechanism is still obscure in some
cases. Here, we suggest an unified approach to investigate segregation and its
effects on the mechanical properties of polycrystalline alloys using the
example of 3 impurities (Mg, Al, Si, P, or S) at a special type tilt grain boundary in Cu. We show that for these impurities
segregating to the grain boundary the strain contribution to the work of grain
boundary decohesion is small and that the chemical contribution correlates with
the electronegativity difference between Cu and the impurity. The strain
contribution to the work of dislocation emission is calculated to be negative,
while the chemical contribution to be always positive. Both the strain and
chemical contributions to the work of dislocation emission generally become
weaker with the increasing electronegativity from Mg to S. By combining these
contributions together we find, in agreement with experimental observations,
that a strong segregation of S can reduce the work of grain boundary separation
below the work of dislocation emission, thus embrittling Cu, while such an
embrittlement cannot be produced by a P segregation because it lowers the
energy barrier for dislocation emission relatively more than for work
separation
Strain-induced stabilization of Al functionalization in graphene oxide nanosheet for enhanced NH3 storage
Strain effects on the stabilization of Al ad-atom on graphene
oxide(GO)nanosheet as well as its implications for NH3 storage have been
investigated using first-principles calculations.The binding energy of Al
ad-atom on GO is found to be a false indicator of its stability.Tensile strain
is found to be very effective in stabilizing the Al ad-atom on GO.It
strengthens the C-O bonds through an enhanced charge transfer from C to O
atoms. Interestingly,C-O bond strength is found to be the correct index for
Al's stability.Optimally strained Al-functionalized GO binds up to 6 NH3
molecules,while it binds no NH3 molecule in unstrained condition.Comment: 11 pages, 3 figures, 4 tables, Applied Physics Letters (Under Review
Statistical analysis of micro-variability properties of the blazar S5 0716+714
The typical blazar S5 0716714 is very interesting due to its rapid and
large amplitude variability and high duty cycle of micro-variability in optical
band. We analyze the observations in I, R and V bands obtained with the
telescope at Weihai observatory of Shandong University from 2011 to 2018. The
model of synchrotron radiation from turbulent cells in a jet has been proposed
as a mechanism for explaining micro-variability seen in blazar light curves.
Parameters such as the sizes of turbulent cells, the enhanced particle
densities, and the location of the turbulent cells in the jet can be studied
using this model. The model predicts a time lag between variations as observed
in different frequency bands. Automatic model fitting method for
micro-variability is developed, and the fitting results of our multi-frequency
micro-variability observations support the model. The results show that both
the amplitude and duration of flares decomposed from the micro-variability
light curves confirm to the log-normal distribution. The turbulent cell size is
within the range of about 5 to 55 AU, and the time lags of the
micro-variability flares between the I-R and R-V bands should be several
minutes. The time lags obtained from the turbulence model are consistent with
the fitting statistical results, and the time lags of flares are correlated
with the time lags of the whole light curve.Comment: 12 pages, 11 figures, Accepted by Ap
Biochar to improve soil fertility. A review
International audienceAbstractSoil mineral depletion is a major issue due mainly to soil erosion and nutrient leaching. The addition of biochar is a solution because biochar has been shown to improve soil fertility, to promote plant growth, to increase crop yield, and to reduce contaminations. We review here biochar potential to improve soil fertility. The main properties of biochar are the following: high surface area with many functional groups, high nutrient content, and slow-release fertilizer. We discuss the influence of feedstock, pyrolysis temperature, pH, application rates, and soil types. We review the mechanisms ruling the adsorption of nutrients by biochar
A new 2D monolayer BiXene, M2C (M=Mo, Tc, Os)
Note this is a rather coarse version of our manuscript since uploading tex
files are necessary (we are not willing to upload all tex files).
The existence of BiXenes, a new family of 2D monolayers is here predicted.
Theoretically, BiXenes have 1H symmetry (P-6m2) and can be formed from the
4d/5d binary carbides. As the name suggests, they are close relatives of
MXenes, which instead have 1T symmetry (P-3m1). The newly found BiXenes, as
well as some new MXenes, are shown to have formation energies close to that of
germanene, which suggests that these materials should be possible to be
synthesised. Among them, we illustrate that 1H-Tc2C and 1T-Mo2C are dynamically
stable at 0 K, while 1H-Mo2C, 1TTc2C, 1H-Tc2C, and 1T-Rh2C are likely to be
stabilised via strain or temperature. In addition, the nature of the chemical
bonding is analysed, emphasizing that the covalency between the transition
metal ions and carbon is much stronger in BiXenes than in MXenes. The emergence
of BiXenes can not only open up a new era of conducting 2D monolayers, but also
provide good candidates for carrier materials aimed at energy storage and
spintronic devices that have already been unveiled in MXenes
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