Unbiased search by first-principles simulated annealing revealed irregular cage configurations for medium-sized B
n clusters (namely, boron fullerene) with n=32-56, which are more stable than the ...previously proposed symmetric cages. The stability of these irregular cages can be understood by the three-center bonds as well as the polygonal holes on the cage surface. The delocalized distribution of molecular orbitals as well as the negative nucleus-independent chemical shifts (NICS) values for each boron cage indicates strong aromaticity.
Abstract 1D structures/patterns (e.g., line defect arrays, 1D Moiré patterns) embedded in 2D materials provide fascinating platforms for exploring versatile intriguing phenomena, for example, 1D ...Luttinger liquids and charge density waves (CDWs). Despite persistent efforts, incorporating periodic 1D patterns into 2D materials remains an ongoing pursuit. Herein, the direct preparation of monolayer 1D‐defect‐induced Co 4 Te 7 superlattices (with periodic Te defect lines in the upper Te layer in 1T‐CoTe 2 ) is reported, on lattice‐matched SrTiO 3 (001) (STO(001)) substrates via molecular beam epitaxy (MBE). Utilizing on‐site scanning tunneling microscopy/spectroscopy (STM/STS) combined with density functional theory (DFT) calculations, the detailed atomic structure of monolayer Co 4 Te 7 is identified, and its formation mechanisms from the synergistic effects of the Co/Te precursor ratio and adlayer‐substrate interfacial coupling are uncovered. The potential flat‐band feature of the monolayer Co 4 Te 7 is also unveiled. This work should hereby offer valuable insights into the engineering of periodic 1D‐defect patterns in 2D materials, as well as the atomic‐scale structure and electronic property characterizations, thus paving ways for their intriguing property investigations.
•The highlight of proposed key distribution method reflects on the scalable key distribution rate (KDR), not limited key distribution distance, and sufficient security compared to key distribution ...strategies of QKD, synchronization of chaotic laser, and fiber channel feature extraction.•The scalable KDR reflects on that the KDR can reach a rate of 100Gbit/s at 100% key consistency rate (KCR) without consideration of the balance of KDR and KCR. And, the KDR can be augmented by extending hardware resources of key distribution.•For distribution distance, synchronized chaotic equation systems are innovatively realized by identical hardware equipment, high dimensional hyperchaotic equation, initial value, and micro interference. The synchronization keeping with micro interference of proposed chaotic systems is obtained based on identical quantified fiber BER feature of legal fiber loop. And, all synchronous operation controls to proposed chaotic systems are guaranteed by deterministic rule of algorithm operation, and are not limited by amplifier or fiber length.•The security reflects on that the key distribution strategy is immunized to many possible attacks.•Furthermore, as far as we concerned, there has not the deterministic rule of algorithm operation based key distribution method. In addition, proposed method has economic value attribute to it can be fast applied at scenarios of security access of PON equipment, key provision for experiment, and long haul security optical communication.
Security key is necessary for data encryption while transmitting amounts of confidential information. For existing strategies of key distribution, it is the primary challenge that the rate and distance limit, insufficient security, and difficulty of deployment. To solve these problems, we propose an accelerated key distribution method for endogenously secure optical communication by synchronized chaotic system based on BER feature of fiber channel. First, synchronized chaotic equation systems are innovatively realized by identical hardware equipment, chaotic equation, initial value, and micro interference. Then, the synchronization keeping with micro interference of proposed chaotic systems are obtained based on identical BER feature of fiber loop. Innovatively, all synchronous operation controls to proposed chaotic systems are guaranteed by deterministic rule of algorithm operation, and are not limited by amplifier or fiber length. Experimental result demonstrates that proposed chaotic systems are synchronized under long term operation. The key distribution rate (KDR) can reach a rate of 100Gbit/s at 100% key consistency rate. And, the KDR can be augmented by extending hardware resources of key distribution. Simulation is conducted to illustrate the security of chaotic systems by the bifurcation diagram, scatter plot diagram, and initial value sensitive phenomenon. NIST security test suite demonstrates that generated secret key sequences pass the test. Moreover, possible attacks are analysed for the security robustness of proposed scheme. The results illustrate proposed system is a reliable, secure and cost-effective solution for high-speed and long-haul key distribution.
Defects are well known to obviously affect the crystal structure and the electronic property of two-dimensional transition-metal dichalcogenides (2D TMDs). Herein, we report the direct identification ...of defects of few layer 2H-TaSe2 on Au foils achieved by chemical vapor deposition and their interactions with charge density wave (CDW) order via scanning tunneling microscopy (STM). Four types of defects in 2H-TaSe2 are revealed by STM images and density functional theory (DFT) simulations, which are Se vacancy in the upper Se layer, Se vacancy in the bottom Se layer facing the substrate, Ta vacancy, and locally inserted 1T-TaSe2. Interestingly, the presence of defects in 2H-TaSe2 layers can mediate the amplitude reduction or vanishing of the CDW order, and abundant defects can even break up the long-range CDW phase into nanodomains. In addition, the amplitude of the CDW order is observed to increase gradually with increasing sample bias voltage in STM imaging, possibly due to the defect-induced electronic density inhomogeneity. Hereby, this work should provide valuable insights for the effects of various defect states on the CDW order in 2D metallic TMDs, thus propelling their intriguing property investigations and the related device applications.
The design of compounds with interesting coordination geometries, exotic oxidation states, and intriguing properties is of fundamental interest in physics, chemistry, and materials science. Herein, ...first-principle swarm-intelligence structure search calculations identify two unconventional stoichiometric KN
2
and KN
4
monolayers, in which the coordination number of K atoms increases from 6 to 12, becoming two-dimensional (2D) metal nitrides with the highest coordination number. Nitrogen motifs in stable K-N monolayers depend on the nitrogen content (
e.g.
, N
2
−
dimer in KN
2
and N
2
0.5−
dimer in KN
4
), and are accompanied by an electronic transition from superconducting to metallic. Intriguingly, the KN
2
monolayer shows a unique superconducting energy gap with a calculated critical temperature (
T
c
) of 4.3 K under ambient conditions. The superconductivity is mainly derived from strong electron-phonon coupling (EPC) of the N 2p electrons and low- and mid-frequency K and N atomic vibrational modes. Our work provides key insight into 2D metal-bearing nitrides and the correlation between non-stoichiometry and conductivity mechanisms.
The design of compounds with interesting coordination geometries, exotic oxidation states, and intriguing properties is of fundamental interest in physics, chemistry, and materials science.
Due to coexistence of huge number of structural isomers, global search for the ground-state structures of atomic clusters is a challenging issue. The difficulty also originates from the computational ...cost of ab initio methods for describing the potential energy surface. Recently, machine learning techniques have been widely utilized to accelerate materials discovery and molecular simulation. Compared to the commonly used artificial neural network, graph network is naturally suitable for clusters with flexible geometric environment of each atom. Herein we develop a cluster graph attention network (CGANet) by aggregating information of neighboring vertices and edges using attention mechanism, which can precisely predict the binding energy and force of silver clusters with root mean square error of 5.4 meV/atom and mean absolute error of 42.3 meV/Å, respectively. As a proof-of-concept, we have performed global optimization of medium-sized Ag n clusters ( n = 14−26) by combining CGANet and genetic algorithm. The reported ground-state structures for n = 14−21, have been successfully reproduced, while entirely new lowest-energy structures are obtained for n = 22−26. In addition to the description of potential energy surface, the CGANet is also applied to predict the electronic properties of clusters, such as HOMO energy and HOMO-LUMO gap. With accuracy comparable to ab initio methods and acceleration by at least two orders of magnitude, CGANet holds great promise in global search of lowest-energy structures of large clusters and inverse design of functional clusters.
•A new group of 2D-RP perovskites with cyclohexane methylamine (CMA) was investigated.•The 2DRPP films can be prepared in air without hot-casting, additives, and glove box.•The efficiency of the CMA ...based solar cells reached 10.66% with excellent stability.•Unencapsulated device retained 95% efficiency when exposed to 60% RH for 1500 h.
Two-dimensional Ruddlesden-Popper perovskites (2D-RPPs) have attracted attention due to their superior moisture stability. In this study, we prepared and characterized a new group of 2D perovskites with cyclohexane methylamine (CMA+) as a spacer cation. The compounds (CMA)2(MA)n−1PbnI3n+1 (n = 1, 2, 3, and 4) showed high self-assembly (where MA is CH3NH3), which allowed for high-quality films to be deposited through the one-step spin-coating method in ambient air. Hot-casting technique, additives, and glove box were not required in the fabrication process. The bandgaps of this group of compounds can be varied from 2.36 eV for (CMA)2PbI4 (n = 1) to 1.52 eV for MAPbI3 (n = ∞) with increasing n value. Moreover, we found that the thin films of (CMA)2(MA)n−1PbnI3n+1 showed considerable stability in moisture and thermal tests. We successfully inserted these new 2D-RPPs in solar cells, and obtained the best power conversion efficiency of 10.66%, with an open-circuit voltage (Voc) of 1.00 V, and a short-circuit current density (Jsc) of 16.99 mA/cm2 for our first-generation device containing (CMA)2(MA)3Pb4I13 (n = 4). The CMA-based devices exhibited superior long-term stability, the unencapsulated (CMA)2(MA)3Pb4I13 solar cell retained nearly 95% of its initial efficiency when exposed to ambient conditions with a 60% relative humidity for 1500 h.
We investigated the atomistic mechanism of He–He and He–metal interactions in bcc transition metals (V, Nb, Ta, Cr, Mo, W, and Fe) using first-principles methods. We calculated formation energy and ...binding energy of He–He pair as function of distance within the host lattices. The strengths of He–He attraction in Cr, Mo, W, and Fe (0.37–1.11 eV) are significantly stronger than those in V, Nb, and Ta (0.06–0.17 eV). Such strong attractions mean that He atoms would spontaneously aggregate inside perfect Cr, Mo, W, and Fe host lattices in absence of defects like vacancies. The most stable configuration of He–He pair is dumbbell in groups VB metals, whereas it adopts close configuration in Cr, Mo, and Fe, and close configuration in W. Overall speaking, the He–He equilibrium distances of 1.51–1.55 Å in the group VIB metals are shorter than 1.65–1.70 Å in the group VB metals. Moreover, the presence of interstitial He significantly facilitates vacancy formation and this effect is more pronounced in the group VIB metals. The present calculations help understand the He-metal/He–He interaction mechanism and make a prediction that He is easier to form He cluster and bubbles in the groups VIB metals and Fe.
