Accepted
,,Received Date:2024-07-31
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Due to the inadequacy of the existing experimental techniques, it is difficult to observe the microstructure evolution during the sintering process in real time, resulting in a lack of in-depth understanding of the sintering mechanism of two-phase composite fuels. Therefore, it is greatly important to carry out theoretical simulation studies on the sintering process of composite fuels. In this work, a phase-field model of the two-phase sintering process of ceramic composite fuel is established, and the sintering process of UN-U3Si2composite fuel is simulated by using this method. The simulation results show that the surface deformation of the grains with higher surface energy is obvious during the formation of sintering neck. The final equilibrium dihedral angle formed by the two-phase double grains depends on the ratios of the grain boundary energy to the surface energy of the two phases. The phenomenon of large grains swallowing small grains do not occur between the two unequal double grains. Subsequently, the pore shrinkage and the properties of the trident grain boundary between the two-phase three-grain are investigated during the sintering process. It is found that the angle of the trident grain boundary formed by the two-phase three-grain deviates from 120°. The high-energy barrier at the grain boundary impedes the diffusion of the pore vacancies along the grain boundary, resulting in a slowdown of the pore shrinkage rate at the trident grain boundary. In addition, the simulation results of the microstructure evolution of two-phase polycrystalline sintered tissue with different volume fraction ratios show that the grain boundary diffusion plays a major role in the two-phase sintering process. The grain growth of the phase with a larger volume fraction is dominant, and the role of hindering the grain boundary migration between the two-phase grains exists. The phenomenon of grain migration exists among grains of the same phase.
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In this work, Gd20+2xHo20-xEr20-xCo20Ni10Al10(x = 0, 5, 10) high-entropy metallic glasses (MGs) with a critical diameter of 2 mm were successfully designed and fabricated by the substitution of Gd, Ho and Er. The effects of types and contents of rare earth (RE) elements on the microstructure, thermodynamic behaviors, and magnetocaloric effect (MCE) were investigated systematically. The amorphous structure of the ribbons and as-cast rods were confirmed by X-ray diffraction (XRD) with CuKα radiation (2θ= 20°-80°). The atomic-scale ordered configurations were examined by using high-resolution transmission electron microscop (HRTEM). Thermal analysis was carried out on differential scanning calorimeter (DSC) with a heating rate of 20 K/min by using ribbons. The magnetic measurements were conducted by using magnetometer in the temperature range of 5-180 K. According to DSC traces, it suggests that as Ho and Er are replaced by Gd, the thermal stability of MGs slightly decreases, e.g., both glass transition temperature (Tg) and initial crystallization temperature (Tx) decrease gradually, meanwhile the liquidus temperature (Tl) increases, which results in a reduction of glass-forming ability criteria such as the reduced glass transition temperaturesTrg(Trg=Tg/T1)、γ(γ=Tx/(Tg+T1))和γm(γm= (2Tx-Tg)/T1), thermodynamically. The analyses based on XRD and HRTEM show that the degree of order in MGs decreases with increasing Gd content, which facilitates the glass formation. The magnetocaloric parameters such as Curie temperature (Tc), maximum magnetic entropy change (|ΔSMpk|) and relative cooling power (RCP) all increase gradually with the addition of Gd. Gd40Ho10Er10CoNiAl exhibits the best refrigeration performance among all studied systems, where the peak value of |ΔSM| is 8.31 J·kg-1·K-1and RCP is 740.82 J·kg-1. The results indicate that MCEs of MGs including RCP,Tcand |ΔSMpk|, mainly depend on the de Gennes factor rather than the effective magnetic moment, while thermodynamic properties are more affected by thef-dhybridization effect. With the increase of 4felectrons, the thermal stability increases with increasing the degreef-dorbital hybridization. In summary, the RE-based MG with high thermal stability and adjustableTccan be achieved by means of the RE substitution via adjusting the number of 4felectrons.
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The primary microstructures in metallic liquids (or supercooled liquids) play a decisive role in determining the final solidification pathway (crystallization or amorphization). However, the question of which specific microstructures play a critical role has attracted widespread attention from scholars. Some previous theoretical and experimental studies have suggested that icosahedron (ICO) clusters (or ICO short-range order) in metallic liquids possess lower energy than crystals, and a high abundance of ICO clusters can increase the nucleation barrier, promoting amorphous transformation. Current research results indicate that the content of various clusters (especially ICO clusters) is low in many metallic liquids. Therefore, it is significant to identify which microstructure plays a critical role in metallic liquids.
In this work, the rapid solidification processes of tantalum (Ta) metallic liquid under various pressure conditions were investigated using molecular dynamic (MD) simulation, the microstructure evolution during different solidification processes is quantitatively analyzed through the average atomic energy, pair distribution function, and largest standard cluster analysis (LaSCA). The results show that, compared to the low content of ICO, topologically close-packed (TCP) clusters are not only more abundant but also play a more decisive role in determining the solidification path of Ta metallic liquids. Under pressureP∈[0, 8.75] GPa, the TCP clusters in Ta metallic liquid exhibit low energy, and a highly stable state as well as highly interconnected and resistant to decomposition, thereby promoting the amorphous transformation of the Ta metallic liquid. Under pressureP∈[9.375, 50] GPa, the TCP clusters in Ta metallic liquid are in a metastable state, many TCP clusters with high energy state can easily transform into other clusters during the liquid-solid transition process. At this stage, nucleation and growth of the body-centered cubic (BCC) embryo primarily occur in areas where TCP clusters are stacked sparsely, eventually forming a perfect BCC crystal from Ta metallic liquid.
In this work, the rapid solidification processes of tantalum (Ta) metallic liquid under various pressure conditions were investigated using molecular dynamic (MD) simulation, the microstructure evolution during different solidification processes is quantitatively analyzed through the average atomic energy, pair distribution function, and largest standard cluster analysis (LaSCA). The results show that, compared to the low content of ICO, topologically close-packed (TCP) clusters are not only more abundant but also play a more decisive role in determining the solidification path of Ta metallic liquids. Under pressureP∈[0, 8.75] GPa, the TCP clusters in Ta metallic liquid exhibit low energy, and a highly stable state as well as highly interconnected and resistant to decomposition, thereby promoting the amorphous transformation of the Ta metallic liquid. Under pressureP∈[9.375, 50] GPa, the TCP clusters in Ta metallic liquid are in a metastable state, many TCP clusters with high energy state can easily transform into other clusters during the liquid-solid transition process. At this stage, nucleation and growth of the body-centered cubic (BCC) embryo primarily occur in areas where TCP clusters are stacked sparsely, eventually forming a perfect BCC crystal from Ta metallic liquid.
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The Ti-2.5Al-2Zr-1Fe used as hull structural material, is susceptible to hydrogen embrittlement induced by corrosion and hydrogen evolution in marine environments. Given the long-term service of ships, the hydrogen embrittlement behavior under slow strain rate is crucial for assessing the alloy's service performance and ensuring long-term ship structural safety. To investigate the hydrogen embrittlement mechanism of Ti-2.5Al-2Zr-1Fe alloy under slow strain rate conditions, this study integrated the use of slow tension and constant displacement loading techniques to systematically evaluate the attenuation of mechanical properties and the dynamic changes in hydrogen embrittlement sensitivity of hydrogen-containing Ti-2.5Al-2Zr-1Fe alloy.Employing Scanning Electron Microscopy (SEM), we conducted a thorough analysis of the microstructural features of fracture surfaces. Simultaneously, Secondary Ion Mass Spectrometry (SIMS) was utilized to elucidate the intimate correlation between the brittle zones at fracture sites and the macroscopic distribution of hydrogen. Additionally, theoretical analysis based on diffusion equations revealed a notable increase in hydrogen diffusion distance within the Ti-2.5Al-2Zr-1Fe alloy as hydrogen charging time increased.Further, leveraging the dislocation-hydrogen interaction model, we derived a critical strain rate threshold ε0= [(30RT)/(ρDE)] for dislocation-mediated hydrogen transport in titanium alloys. When the externally applied strain rate ε falls below this threshold, dislocations efficiently capture and transport hydrogen atoms, enhancing hydrogen diffusion depth and significantly augmenting the alloy's hydrogen embrittlement sensitivity, thereby accelerating material embrittlement.Vickers Hardness (HV) testing further illuminated the dual nature of hydrogen's influence on titanium alloy properties: while moderate hydrogen content slightly enhances surface hardness, exceeding a specific threshold leads to a dominant negative impact on plasticity, vastly outweighing the benefits of surface hardening and resulting in a substantial decline in overall mechanical performance.To comprehensively decipher the hydrogen embrittlement mechanism of Ti-2.5Al-2Zr-1Fe alloy, Transmission Electron Microscopy (TEM) was employed to analyze the phase composition in regions of high hydrogen concentration, crack tips, and their vicinities. The analysis results indicate that no direct precipitation of hydrides was observed; instead, hydrogen preferentially accumulated in the β-phase, prompting microcrack propagation along β-phase boundaries.Based on the aforementioned experimental data and microstructural analysis, we propose that the hydrogen embrittlement mechanism in Ti-2.5Al-2Zr-1Fe alloy is primarily governed by the HEDE mechanism. Furthermore, when the strain rate falls below ε0, it synergizes with the dislocation-mediated hydrogen transport mechanism, vastly expanding the influence scope of the HEDE mechanism and exacerbating the alloy's hydrogen embrittlement sensitivity.
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Carrier mobility is a key parameter determining the response speed of charge carriers to electric fields in nanoelectronic devices. This study aims to explore the charge carrier transport properties of monolayer IrSCl and IrSI. Using first-principles calculations based on density functional theory (DFT), we systematically investigated the electronic structure and transport properties of monolayer IrSCl and IrSI. Phonon dispersion calculations indicate that both IrSCl and IrSI exhibit no imaginary frequencies, confirming their structural stability. Furthermore, molecular dynamics simulations demonstrate that these materials maintain thermal stability at room temperature (300 K). Evaluating the bandgap using the Perdew-Burke-Ernzerhof (PBE) functional and the hybrid HSE06 functional shows that both IrSCl and IrSI are indirect bandgap semiconductors. The bandgap values for monolayer IrSCl are 0.37 eV (PBE) and 1.58 eV (HSE06), while those for monolayer IrSI are 0.23 eV (PBE) and 1.36 eV (HSE06). We further investigated the effects of biaxial tensile strain on the bandgap, revealing that the bandgap of IrSCl and IrSI decreases with increasing strain, reaching 0.05 eV and 0.01 eV (PBE) at a strain of 6%, indicating a strain-induced transition to metallic behavior. Based on deformation potential theory and the Boltzmann transport equation, we calculated the carrier mobilities of monolayer IrSCl and IrSI. The predicted maximum carrier mobility for monolayer IrSCl at room temperature is 407.77 cm2V-1s-1, while that for monolayer IrSI is 202.64 cm2V-1s-1. Additionally, results from the Boltzmann transport equation show that the highest mobilities for IrSCl and IrSI are 299.15 cm2V-1s-1and 286.41 cm2V-1s-1, respectively. These findings suggest that both IrSCl and IrSI possess favorable electronic and transport properties, making them promising candidates for future applications in two-dimensional nanoelectronic devices. Notably, the combination of a moderate bandgap and high carrier mobility at room temperature indicates their potential use in transistors, sensors, and other electronic components. This study provides valuable insights into the material properties of IrSCl and IrSI, contributing to the design of novel two-dimensional materials for electronic applications.
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To investigate the impact of group behavior on pedestrian evacuation under zero-visibility conditions, this paper combines controlled experiments with modeling and simulation for an in-depth analysis. Initially, by organizing experiments on pedestrian evacuation under zero-visibility conditions, the research identifies typical evacuation behaviors such as group behavior, auditory guidance behavior, and wall-following behavior. The pedestrians rely on auditory information to guide their companions during the process of forming groups. Pedestrian group behavior can be divided into three modes, and the walking speeds of grouped pedestrians vary depending on their spatial positions. By comparing and analyzing the walking speed and evacuation time of pedestrians under different grouping modes, it is found that group behavior under zero-visibility conditions reduces evacuation efficiency, while walking along the walls can improve evacuation efficiency. Subsequently, considering the movement characteristics of pedestrians in different group behavior modes, the influence mechanisms of auditory guidance and wall-following behavior on the evacuation process, a pedestrian evacuation model based on cellular automata under zero-visibility conditions is developed. Finally, the proposed model is validated using experimental results, and simulations are conducted to analyze the impact of group behavior on the evacuation process under zero-visibility conditions. By comparing and analyzing pedestrian movement trajectories and evacuation times in both the simulation and experimental processes, it is verified that the model can effectively reproduce the group evacuation process of pedestrians under zero-visibility conditions. When auditory guidance errors are considered, pedestrians exhibit wandering behavior in their movement trajectories. During the evacuation process, the greater the distance pedestrians can perceive each other for grouping, the higher the probability of group formation. As a result, groups are formed earlier, which decreases evacuation efficiency. This indicates that under zero-visibility conditions, group behavior negatively impacts the evacuation process. This research provides a scientific basis for the formulation of pedestrian evacuation strategies and plans in similar scenarios.
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Recently, researchers have proven that an infinite number of Charlies and a pair of Alice and Bob can share standard tripartite nonlocality and genuinely nonsignal nonlocality by violating the Mermin and NS inequalities within tripartite systems. This discovery undoubtedly offers new perspectives and potential in quantum information science. However, it should be noted that the result is derived under the highly idealized assumption that the quantum system is perfect and free from external disturbances. In practice, the realization of this ideal state is a challenging proposition. As a fundamental aspect of quantum mechanics, the phenomenon of quantum entanglement is susceptible to the influence of external factors, such as noise, during its practical implementation. Additionally, the process of quantum measurement can introduce potential errors, which may potentially diminish or even negate the observed quantum nonlocality. In light of the above, we examine whether the corresponding quantum nonlocality can be shared indefinitely despite the inevitable occurrence of noise and error. The aim of this paper is to examine and discuss the persistency of nonlocality in the context of noisy three-qubit systems. In the initial phase of the study, sufficient conditions are provided for Alice and Bob to share standard tripartite nonlocality with any number of Charlies, even when measurements are noisy and the initial three-qubit system is in a maximally entangled state with noise. This finding indicates that certain standard tripartite nonlocality can persist under non-ideal conditions as long as certain conditions are met. Moreover, the article elucidates the requisite conditions for multiple independent Charlies to share genuinely nonsignal nonlocality with a pair of Alice and Bob in a non-ideal state. This implies that, despite the presence of noise and errors, this type of genuinely nonsignal nonlocality can still be securely shared among multiple parties as long as specific conditions are met. This provides a new theoretical basis for the security and feasibility of quantum communication. In conclusion, the comprehensive analysis presented in this paper offers insights into the behaviour of triple quantum nonlocality under noiseless conditions.
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The study of high-precision spectroscopy for hydrogen molecular ions enables the determination of fundamental constants, such as the proton-to-electron mass ratio, the deuteron-to-electron mass ratio, the Rydberg constant, and the charge radii of proton and deuteron. This can be accomplished through a combination of high precision experimental measurements and theoretical calculations. The spectroscopy of hydrogen molecular ions reveals abundant hyperfine splittings, necessitating not only an understanding of rovibrational transition frequencies but also a thorough grasp of hyperfine structure theory to extract meaningful physical information from the spectra. This article reviews the history of experiments and theories related to the spectroscopy of hydrogen molecular ions, with a particular focus on the theory of hyperfine structure. As far back as the second half of the last century, the hyperfine structure of hydrogen molecular ions was described by a comprehensive theory based on its leading-order term, known as the Breit-Pauli Hamiltonian. Thanks to the advancements in non-relativistic quantum electrodynamics (NRQED) at the beginning of this century, a systematic development of next-to-leading-order theory for hyperfine structure has been achieved and applied to H2+and HD+in recent years, including the establishment of themα7ln(α) order correction. For the hyperfine structure of H2+, theoretical calculations show good agreement with experimental measurements after decades of work. However, for HD+, discrepancies have been observed between measurements and theoretical predictions that cannot be accounted for by the theoretical uncertainty in the non-logarithmic term of themα7order correction. To address this issue, additional experimental measurements are needed for mutual validation, as well as independent tests of the theory, particularly regarding the non-logarithmic term of themα7order correction.
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Photoelectron spectroscopy serves as a prevalent characterization technique within the realm of material science. Specifically, angle-resolved photoelectron spectroscopy (ARPES) provides a direct method for determining the energy-momentum dispersion relationship and Fermi surface structure of electrons within a material system. This makes ARPES a potent tool for the investigation of many-body interactions and correlated quantum materials. The field of photoelectron spectroscopy has seen continuous advancements, with the emergence of technologies such as time-resolved ARPES and nano-ARPES. Concurrently, the evolution of synchrotron radiation devices has led to the generation of an increasing volume of high throughput and high dimension experimental data. This underscores the growing urgency for the development of more efficient and precise data processing methods, as well as the extraction of deeper physical information. In light of these developments, machine learning is poised to play an increasingly significant role across various fields, including but not limited to ARPES. This paper reviews the application of machine learning in photoelectron spectroscopy, which primarily encompasses three aspects:
1.Data Denoising: Machine learning can be utilized for denoising photoelectron spectroscopy data. The denoising process via machine learning algorithms can be bifurcated into two methods. Both of the two methods do not need for manual data annotation. The first approach involves the use of noise generation algorithms to simulate experimental noise, thereby obtaining effective low signal-to-noise ratio to high signal-to-noise ratio data pairs. Alternatively, the second approach can be employed to extract noise and clean spectral data, respectively.
2.Electronic Structure and Chemical Composition Analysis: Machine learning can be applied for the analysis of electronic structure and chemical composition. (Angle-resolved) photoelectron spectroscopy contains abundant information about material structure. Information such as energy band structure, self-energy, binding energy, and other condensed matter data can be rapidly acquired through machine learning schemes.
3.Prediction of Photoelectron Spectroscopy: the electronic structure information obtained by combining first-principles calculation can also predict the photoelectron spectroscopy. The rapid acquisition of photoelectron spectroscopy data through machine learning algorithms also holds significance for material design. Photoelectron spectroscopy holds significant importance in the study of condensed matter physics. In the context of synchrotron radiation development, the construction of an automated data acquisition and analysis system could play a pivotal role in condensed matter physics research. In addition, adding more physical constraints to the machine learning model will improve the interpretability and accuracy of the model. There exists a close relationship between photoelectron spectroscopy and first-principles calculations with respect to electronic structure properties. The integration of these two through machine learning is anticipated to significantly contribute to the study of electronic structure properties. Furthermore, as machine learning algorithms continue to evolve, the application of more advanced machine learning algorithms in photoelectron spectroscopy research is expected. By building automated data acquisition and analysis systems, designing comprehensive workflows based on machine learning and first-principles methods, and integrating new machine learning techniques, it will help accelerate the progress of photoelectron spectroscopy experiments and facilitate the analysis of electronic structure properties and microscopic physical mechanisms, which will advance the frontier research in quantum materials and condensed matter physics.
1.Data Denoising: Machine learning can be utilized for denoising photoelectron spectroscopy data. The denoising process via machine learning algorithms can be bifurcated into two methods. Both of the two methods do not need for manual data annotation. The first approach involves the use of noise generation algorithms to simulate experimental noise, thereby obtaining effective low signal-to-noise ratio to high signal-to-noise ratio data pairs. Alternatively, the second approach can be employed to extract noise and clean spectral data, respectively.
2.Electronic Structure and Chemical Composition Analysis: Machine learning can be applied for the analysis of electronic structure and chemical composition. (Angle-resolved) photoelectron spectroscopy contains abundant information about material structure. Information such as energy band structure, self-energy, binding energy, and other condensed matter data can be rapidly acquired through machine learning schemes.
3.Prediction of Photoelectron Spectroscopy: the electronic structure information obtained by combining first-principles calculation can also predict the photoelectron spectroscopy. The rapid acquisition of photoelectron spectroscopy data through machine learning algorithms also holds significance for material design. Photoelectron spectroscopy holds significant importance in the study of condensed matter physics. In the context of synchrotron radiation development, the construction of an automated data acquisition and analysis system could play a pivotal role in condensed matter physics research. In addition, adding more physical constraints to the machine learning model will improve the interpretability and accuracy of the model. There exists a close relationship between photoelectron spectroscopy and first-principles calculations with respect to electronic structure properties. The integration of these two through machine learning is anticipated to significantly contribute to the study of electronic structure properties. Furthermore, as machine learning algorithms continue to evolve, the application of more advanced machine learning algorithms in photoelectron spectroscopy research is expected. By building automated data acquisition and analysis systems, designing comprehensive workflows based on machine learning and first-principles methods, and integrating new machine learning techniques, it will help accelerate the progress of photoelectron spectroscopy experiments and facilitate the analysis of electronic structure properties and microscopic physical mechanisms, which will advance the frontier research in quantum materials and condensed matter physics.
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White LEDs have a broad application prospects and market demand, while the red phosphor play a big impact on the color temperature and color rendering index of the modulated white light. In this paper, a series of Li2Gd4-xSmx(MoO4)7(x=0.01-0.13) phosphors were prepared by high temperature solid phase method. The successful doping of Sm3+into Li2Gd4(MoO4)7was confirmed by X-ray diffractometry (XRD) and did not result in any change in crystal structure. The samples were detected by scanning electron microscope (SEM) as irregular blocky structures with particle size less than 20μm. The presence of Li, Gd, Mo, O and Sm elements in the phosphor was confirmed by energy dispersive X-ray spectroscopy (EDS). X-ray photoelectron spectroscopy (XPS) studies showed that the activator was successfully doped into materials. Under 406 nm excitation, the emission peaks of the sample are located at 563, 598, 645 and 706nm respectively, which are caused by the 4f-4ftransition of Sm3+and the strongest emission peak comes from4G5/2→6H9/2transition. It was found that optimal concentration of Sm3+is 0.07. With the increase of Sm3+concentration, the fluorescence lifetime decreases gradually. The temperature-dependent emission of phosphor was also studied. The emission intensity at 473 K was still 79% of that at 298 K, indicating that the sample had excellent heat resistance. The CIE chromaticity diagram shows the luminescence of the prepared phosphor is located in the orange-red region and the color purity is high (99%). Moreover, a white LED is manufactured using the optical doped phosphor, which has CIE coordinates of (0.3788, 0.3134) and is located in the circle of white light. Research shows that Li2Gd4(MoO4)7: Sm3+phosphor is a promising orange-red phosphor for white LEDs.
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Half-band-gap turn-on characteristic is a unique photoelectric property of organic light-emitting diodes (OLEDs), which has advantage in the development of low power consumption devices. But the physical mechanism that the electron injection layer (EIL) affects the half-band-gap turn-on characteristics has not been reported. Herein, we found that the change from half-band-gap turn-on electroluminescence (EL) to sub-band-gap turn-on EL to normal turn-on EL is observed by tuning the electron mobility of EIL in Rubrene/C60 based devices. Three sets of devices were fabricated by using BCP (~10-3cm2·V–1·s–1, Dev.1), Bphen (~10-4cm2·V–1·s–1, Dev.2) and TPBi (~10-5cm2·V–1·s–1, Dev.3) as EIL materials. By measuring theI-B-Vcurves of devices at room temperature, we found that the turn-on voltage of devices obviously increases with the decreases of electron mobility of EIL by an order of magnitude. Specifically, the turn-on voltage of Dev.1, Dev.2, and Dev.3 exhibit the physical phenomena of half-band-gap turn-on (1.1 V), sub-band-gap turn-on (2.1 V) and normal turn-on (4.1 V) properties, respectively. The magneto-electroluminescence (MEL) results show that the half-band-gap turn-on characteristic of high EIL electron mobility (Dev.1) is attributed to the triplet-triplet annihilation (TTA, T1, Rb+ T1, Rb→ S1, Rb+ S0) process which can effectively reduce the turn-on voltage. However, the half-band-gap turn-on characteristic is not observed in the devices (Dev.2 and Dev.3) with low carrier mobility, which can be reasonably explained by a higher voltage is applied to the EIL with low electron mobility in order to inject more electrons. The higher voltage counteracts the reduced turn-on voltage of the TTA process, resulting in Dev.2 and Dev.3 with sub-band-gap turn-on and normal turn-on, respectively. In addition, although the TTA process was observed in all three devices, the TTA process was stronger and the EL was higher in Dev.1 with high EIL electron mobility. This is because a large number of triplet Rubrene/C60 exciplex states (EX3) was formed at the Rubrene/C60 interface, enhancing the Dexter energy transfer (DET, EX3→ T1, Rb) process from EX3to triplet exciton of Rubrene (T1, Rb). That is, Dev.1 exhibits stronger TTA process and higher EL due to the presence of a large number of T1, Rbexciton formed by DET process as compared to Dev.2 and Dev.3. Furthermore, by measuring theI-Vcurves of devices acquired at low temperature, it was found that the reduced carrier mobility caused by lowering operational temperature increases the turn-on voltages of these three devices. The significantly different increases in the turn-on voltage of Dev.1-3 at the same low temperature is due to the different influences of temperature on the electron mobility of EIL. The tradeoff between the decrease of carrier mobility and the extension of exciton lifetime makes the MEL curves present different temperature-dependent behavior. Obviously, this work further deepens the understanding for the influence of EIL electron mobility on the turn-on voltage and the related physical microscopic mechanism in Rubrene/C60 devices.
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The performances of beryllium-doped graphdiyne (GDY) as an anode material for lithium-ion batteries at various doping sites are investigated by first-principles methods based on density functional theory. Calculations of the formation and cohesive energies of GDY at different doping concentrations indicate that beryllium-doped GDY has excellent prospects for experimental synthesis. More importantly, the beryllium-doped GDY exhibits good electrical conductivity. The adsorption energy for a single lithium atom on beryllium-doped GDY is -4.22 eV, which is significantly higher than that of boron, nitrogen-doped GDY, and intrinsic GDY. As the number of stored lithium atoms increases, the adsorption energy remains greater than the cohesive energy of solid lithium, and the average open-circuit voltage stays between 0-1 V, ensuring the safety of the battery. Additionally, the lithium storage capacity is increased to 881 mAh/g, which is 1.14 times that of undoped GDY and 2.36 times that of graphite. Meanwhile, the diffusion performance of lithium on beryllium-doped GDY is also enhanced. For the CIIIsite doping system, by studying the ion transport at low, medium, and high lithium concentrations, we find that as the lithium concentration increases, the diffusion barriers are 0.38, 0.44, and 0.77 eV, respectively, making lithium ion movement more difficult, but still superior to other element-doped GDY. In summary, beryllium-doped GDY has great potential as an outstanding anode material for lithium-ion batteries.
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Fractional quantum Hall (FQH) states with fractionalzed quasiparticles are exotic topologically ordered quantum states driven by strong correlation between particles. Since the first discovery in 1982 in two-dimensional electron gases penetrated by strong magnetic fields, FQH physics has become an attractive frontier of condensed matter physics. From the last year, several research groups have reported observations of FQH transport at zero magnetic field in moiré superlattices based on transition metal dichalcogenides (TMD) and graphene. Moreover, evidence of fractional quantum spin Hall effect was also reported in TMD moiré superlattices. These results demonstrate that moiré superlattices are ideal platforms to control band structure and interactions to realize fractionalized topological states without external magnetic fields. In this paper, we will briefly review the recent progress. We will also summarize the remaining challenges and discuss the possible future development in this field.
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The asymmetric origin of matter and antimatter in the universe is an important unsolved mystery in science today. In this paper, we briefly review the history of antimatter research and the recent international hotspots of related research. It focuses on the advances in antimatter research made in recent years at the large-scale international RHIC-STAR experiment at the Relativistic Heavy Ion Collider, including the discovery of the first antimatter hypernucleus (anti-hypertriton), antimatter helium 4 and anti-hyperhydrogen 4, the first measurements of antiproton interactions, and the precise measurements of the masses and binding energies of the hypertriton and anti-hypertriton. The antimatter hypertriton nucleus, composed of an antiproton, an antineutron, and an anti-Λ hyperon, is the first anti-hypernucleu to be discovered, extending the three-dimensional nuclide map from the anti-strange quark degree of freedom. Antimatter Helium 4 is the heaviest stable antimatter nucleus yet discovered. Anti-hyperhydrogen 4, just discovered in 2024, is composed of an antiproton, two antineutrons, and an anti-Λ hyperon, and is the heaviest antimatter hypernucleus to date. Equivalence to the proton-proton interaction was established by measurements of the antiproton-antiproton interaction. At the same time, precise measurements of the masses of the hypertriton and anti-hypertriton nuclei confirmed the equivalence of matter and antimatter. And these also fully demonstrate that the CPT symmetry is also valid for antimatter nuclei. Measurements of the binding energy of the hypertriton nucleus indicate that the interaction between Λ and the nucleus of the hypertriton (the deuterium nucleus) is strong, which differs from the earlier common belief that the hypertriton nucleus is a weakly bound system. Furthermore, we discuss different physical mechanisms for the production of (anti)light nuclei, mainly including thermal, coalescence and relativistic kinetic models. Finally, we also present recent results from antihydrogen atom experiments at CERN, antimatter space probes, etc., and discuss the implications of these advances for understanding the structure of matter. In general, current studies of antimatter nuclei and atoms do not yet provide clear evidence for the asymmetric origin of matter and antimatter in the Universe, which pushes to further improve the precision of various types of measurements in the study of antimatter. Of course, other efforts in this direction in nuclear and particle physics are well expected.
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