3,089 research outputs found
Computational Design of Flexible Electride with Nontrivial Band Topology
Electrides, with their excess electrons distributed in crystal cavities playing the role of anions, exhibit a variety of unique electronic and magnetic properties. In this work, we employ the first-principles crystal structure prediction to identify a new prototype of A3B electride in which both interlayer spacings and intralayer vacancies provide channels to accommodate the excess electrons in the crystal. This A3B type of structure is calculated to be thermodynamically stable for two alkaline metals oxides (Rb3O and K3O). Remarkably, the unique feature of multiple types of cavities makes the spatial arrangement of anionic electrons highly flexible via elastic strain engineering and chemical substitution, in contrast to the previously reported electrides characterized by a single topology of interstitial electrons. More importantly, our first-principles calculations reveal that Rb3O is a topological Dirac nodal line semimetal, which is induced by the band inversion at the general electronic k momentums in the Brillouin zone associated with the intersitial electric charges. The discovery of flexible electride in combining with topological electronic properties opens an avenue for electride design and shows great promises in electronic device applications
Old Story New Tell: The Graphite to Diamond Transition Revisited
Graphite and diamond are two well-known allotropes of carbon with distinct
physical properties due to different atomic connectivity. Graphite has a
layered structure in which the honeycomb carbon sheets can easily glide, while
atoms in diamond are strongly bonded in all three dimensions. The transition
from graphite to diamond has been a central subject in physical science. One
way to turn graphite into diamond is to apply the high pressure and high
temperature (HPHT) conditions. However, atomistic mechanism of this transition
is still under debate. From a series of large-scale molecular dynamics (MD)
simulations, we report a mechanism that the diamond nuclei originate at the
graphite grain boundaries and propagate in two preferred directions. In
addition to the widely accepted [001] direction, we found that the growth along
[120] direction of graphite is even faster. In this scenario, cubic diamond
(CD) is the kinetically favorable product, while hexagonal diamond (HD) would
appear as minor amounts of twinning structures in two main directions.
Following the crystallographic orientation relationship, the coherent interface
t-(100)gr//(11-1)cd + [010]gr//[1-10]cd was also confirmed by high-resolution
transmission electron microscopy (HR-TEM) experiment. The proposed phase
transition mechanism does not only reconcile the longstanding debate regarding
the role of HD in graphite-diamond transition, but also yields the atomistic
insight into microstructure engineering via controlled solid phase transition.Comment: 35 pages, 5 figure
One-shot ultraspectral imaging with reconfigurable metasurfaces
One-shot spectral imaging that can obtain spectral information from thousands
of different points in space at one time has always been difficult to achieve.
Its realization makes it possible to get spatial real-time dynamic spectral
information, which is extremely important for both fundamental scientific
research and various practical applications. In this study, a one-shot
ultraspectral imaging device fitting thousands of micro-spectrometers (6336
pixels) on a chip no larger than 0.5 cm, is proposed and demonstrated.
Exotic light modulation is achieved by using a unique reconfigurable
metasurface supercell with 158400 metasurface units, which enables 6336
micro-spectrometers with dynamic image-adaptive performances to simultaneously
guarantee the density of spectral pixels and the quality of spectral
reconstruction. Additionally, by constructing a new algorithm based on
compressive sensing, the snapshot device can reconstruct ultraspectral imaging
information (/~0.001) covering a broad (300-nm-wide)
visible spectrum with an ultra-high center-wavelength accuracy of 0.04-nm
standard deviation and spectral resolution of 0.8 nm. This scheme of
reconfigurable metasurfaces makes the device can be directly extended to almost
any commercial camera with different spectral bands to seamlessly switch the
information between image and spectral image, and will open up a new space for
the application of spectral analysis combining with image recognition and
intellisense
Enhance Primordial Black Hole Abundance through the Non-linear Processes around Bounce Point
The non-singular bouncing cosmology is an alternative paradigm to inflation,
wherein the background energy density vanishes at the bounce point, in the
context of Einstein gravity. Therefore, the non-linear effects in the evolution
of density fluctuations () may be strong in the bounce phase,
which potentially provides a mechanism to enhance the abundance of primordial
black holes (PBHs). This article presents a comprehensive illustration for PBH
enhancement due to the bounce phase. To calculate the non-linear evolution of
, the Raychaudhuri equation is numerically solved here. Since the
non-linear processes may lead to a non-Gaussian probability distribution
function for after the bounce point, the PBH abundance is
calculated in a modified Press-Schechter formalism. In this case, the criterion
of PBH formation is complicated, due to complicated non-linear evolutionary
behavior of during the bounce phase. Our results indicate that
the bounce phase indeed has potential to enhance the PBH abundance
sufficiently. Furthermore, the PBH abundance is applied to constrain the
parameters of bounce phase, providing a complementary to the surveys of cosmic
microwave background and large scale structure.Comment: 17 pages, 6 figure
Strength-dependent Transition of Graphite Under Shock Condition Resolved by First Principles
The shock strength dependent formation of diamond represents one of the most
intriguing questions in graphite research. Using ab initio DFT-trained carbon
GNN model, we observe a strength-dependent graphite transition under shock. The
poor sliding caused by scarce sliding time under high-strength shock forms
hexagonal diamond with an orientation of (001)G//(100)HD+[010]G//[010]HD; under
low-strength shock, cubic diamond forms after enough sliding time, unveiling
the strength-dependent graphite transition. We provide computational evidence
of the strength-dependent graphite transition from first principles, clarifying
the long-term shock-induced hexagonal formation and structural
strength-dependent trend source
Hybrid GRU-CNN Bilinear Parameters Initialization for Quantum Approximate Optimization Algorithm
The Quantum Approximate Optimization Algorithm (QAOA), a pivotal paradigm in
the realm of variational quantum algorithms (VQAs), offers promising
computational advantages for tackling combinatorial optimization problems.
Well-defined initial circuit parameters, responsible for preparing a
parameterized quantum state encoding the solution, play a key role in
optimizing QAOA. However, classical optimization techniques encounter
challenges in discerning optimal parameters that align with the optimal
solution. In this work, we propose a hybrid optimization approach that
integrates Gated Recurrent Units (GRU), Convolutional Neural Networks (CNN),
and a bilinear strategy as an innovative alternative to conventional optimizers
for predicting optimal parameters of QAOA circuits. GRU serves to
stochastically initialize favorable parameters for depth-1 circuits, while CNN
predicts initial parameters for depth-2 circuits based on the optimized
parameters of depth-1 circuits. To assess the efficacy of our approach, we
conducted a comparative analysis with traditional initialization methods using
QAOA on Erd\H{o}s-R\'enyi graph instances, revealing superior optimal
approximation ratios. We employ the bilinear strategy to initialize QAOA
circuit parameters at greater depths, with reference parameters obtained from
GRU-CNN optimization. This approach allows us to forecast parameters for a
depth-12 QAOA circuit, yielding a remarkable approximation ratio of 0.998
across 10 qubits, which surpasses that of the random initialization strategy
and the PPN2 method at a depth of 10. The proposed hybrid GRU-CNN bilinear
optimization method significantly improves the effectiveness and accuracy of
parameters initialization, offering a promising iterative framework for QAOA
that elevates its performance
The Effects of Modified Simiao Decoction in the Treatment of Gouty Arthritis: A Systematic Review and Meta-Analysis
The modified Simiao decoctions (MSD) have been wildly applied in the treatment of gouty arthritis in China. However, the evidence needs to be evaluated by a systematic review and meta-analysis. After filtering, twenty-four randomised, controlled trials (RCTs) comparing the effects of MSD and anti-inflammation medications and/or urate-lowering therapies in patients with gouty arthritis were included. In comparison with anti-inflammation medications, urate-lowering therapies, or coadministration of anti-inflammation medications and urate-lowering therapies, MSD monotherapy significantly lowered serum uric acid (p<0.00001, mean difference = −90.62, and 95% CI [−128.38, −52.86]; p<0.00001, mean difference = −91.43, and 95% CI [−122.38, −60.49]; p=0.02, mean difference = −40.30, and 95% CI [−74.24, −6.36], resp.). Compared with anti-inflammation medications and/or urate-lowering therapies, MSD monotherapy significantly decreased ESR (p<0.00001; mean difference = −8.11; 95% CI [−12.53, −3.69]) and CRP (p=0.03; mean difference = −3.21; 95% CI [−6.07, −0.36]). Additionally, the adverse effects (AEs) of MSD were fewer (p<0.00001; OR = 0.08; 95% CI [0.05, 0.16]). MSD are effective in the treatment of gouty arthritis through anti-inflammation and lowering urate. However, the efficacy of MSD should be estimated with more RCTs
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