Vol. 74, No. 12 (2025)
2025-06-20
INVITED REVIEW
2025, 74 (12): 120301.
doi: 10.7498/aps.74.20250322
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SPECIAL TOPIC—Atomic, molecular and materials properties data
2025, 74 (12): 120702.
doi: 10.7498/aps.74.20250127
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2025, 74 (12): 123101.
doi: 10.7498/aps.74.20250380
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Carbon monoxide cation (CO+) plays a dominant role in some astrophysical atmosphere environments, and theoretical research on its opacity is crucial for modeling radiative transport. In this work, based on experimentally observed vibrational energy levels of the X2Σ+, A2Π, and B2Σ+ electronic states of CO+, the potential energy curves are improved and constructed using a modified Morse (MMorse) potential function, then the vibrational energy levels and spectroscopic constants are extracted. In the meantime, the internally contracted multireference configuration interaction (MRCI) method with Davison size-extensivity correction (+Q) is used to calculate the potential energy curves and transition dipole moments. The refined MMorse potential shows excellent agreement with the computed potential energy curves, while the spectroscopic constants and vibrational levels indicate strong consistency with existing theoretical and experimental data. The opacities of the CO+ molecule is computed at different temperatures under the pressure of 100 atm. The result shows that as temperature rises, the opacities of transitions in the long-wavelength range increases because of the larger population on excited electronic states at higher temperatures. All the data presented in this paper are openly available at https://doi.org/10.57760/sciencedb.j00213.00136 .
2025, 74 (12): 123102.
doi: 10.7498/aps.74.20250510
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The electronic structure of the ICl+ molecular ion is investigated by using high-level multireference configuration interaction (MRCI) method. To improve computational accuracy, Davidson corrections, spin-orbit coupling (SOC), and core-valence electron correlations effects are incorporated into the calculations. The potential energy curves (PECs) of 21 Λ-S states associated with the two lowest dissociation limits I+(1Dg)+Cl(2Pu) and I+(3Pg)+Cl(2Pu) are obtained. The dipole moments (DMs) of the 21 Λ-S states of ICl+ are systematically studied, and the variations of DMs of the identical symmetry state (22Σ+/32Σ+ and 22Π/32Π) in the avoided crossing regions are elucidated by analyzing the dominant electronic configuration. When considering the SOC effect, the Λ-S states with the same Ω components may form new avoided crossing point, making the PECs more complex. With the help of calculated SOC matrix element, the interaction between crossing states can be elucidated. Spin-orbit coupling matrix elements involving the 22Π, 32Π, 12Δ and 22Δ states are calculated. By analyzing potential energy curves of these states and the nearby electronic states, the possible predissociation channels for 22Π, 32Π, 12Δ and 22Δ states are provided. Based on the computed PECs, the spectroscopic constants of bound Λ-S and Ω states are determined. The comparison of the spectroscopic constants between Λ-S and Ω states indicates that the SOC effect has an obvious correction to the spectroscopic properties of low-lying states. Finally, the transition properties between excited states and the ground state are studied. Based on the computed transition dipole moments and Franck-Condon factors, radiative lifetimes for the low-lying vibrational levels of excited states are evaluated. All the data presented in this paper are openly available at https://doi.org/10.57760/sciencedb.j 00213.00140 .
2025, 74 (12): 125202.
doi: 10.7498/aps.74.20250301
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2025, 74 (12): 127102.
doi: 10.7498/aps.74.20250352
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Metallic materials are widely used in the industrial field due to their excellent electrical transport properties and superior thermal dissipation performance. However, experimental measurements of electrical and thermal conductivity under high-temperature and high-pressure conditions are challenging and costly. This makes numerical simulation an efficient alternative solution. In this study, we develop a computational software named TREX (TRansport at EXtremes). It is based on the Kubo-Greenwood (KG) formula combined with first-principles molecular dynamics. This software is used to calculate electrical conductivity and electronic thermal conductivity. Using magnesium and magnesium-aluminum alloy AZ31B as research subjects, we systematically investigate their electrical and thermal transport properties. The temperature and pressure are in a range of 300−1200 K and 0−50 GPa, respectively. The method involves using first-principles molecular dynamics simulations to obtain equilibrium configurations of high-temperature disordered structures. Electrical conductivity and electronic thermal conductivity are calculated using the KG formula. Lattice thermal conductivity is determined by the Slack equation. To validate the reliability of our approach, we perform comparative calculations by using the Boltzmann transport equation. The research results are cross-verified with experimental data from Sichuan University and the Aerospace Materials Test and Analysis Center. The findings demonstrate that the maximum relative error between computational and experimental results is within 20%. This confirms the accuracy of our method. Additionally, we elucidate the variation patterns of electrical and thermal conductivity in magnesium and AZ31B alloy with temperature and pressure. These patterns include the reduction in electrical conductivity due to aluminum doping, the significant enhancement of conductivity under high pressure, and the unique temperature-induced thermal conductivity enhancement in AZ31B alloy. The TREX program developed in this study and the established performance dataset provide essential tools and data support. They are useful for research on electrical and thermal transport mechanisms in metallic materials under extreme conditions, and also for engineering applications. All the data presented in this paper are openly available at https://www.doi.org/10.57760/sciencedb.j00213.00128.
GENERAL
2025, 74 (12): 120201.
doi: 10.7498/aps.74.20250305
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2025, 74 (12): 120501.
doi: 10.7498/aps.74.20241501
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Detonation test is affected by small experimental datasets due to high risk of implementation and the huge cost of sample production and measurement. The major challenges of limited data consist in constructing the probability distribution of physical quantities and application of machine learning. Probability learning on manifold (PLoM) can generate a large number of implementations that are consistent with practical common knowledge, while preserving potential physical mechanism these generated samples. So PLoM is viewed as an efficient tool of tackling small samples. To begin with, experimental data are assumed to be concentrated on an unknown subset of Euclidean space and can be treated as the sampling of random vector to be determined. Meanwhile, experimental problem is solved in the framework of matrix and the scaling transformation is conducted on the datasets of PBX9502 with multi-physics attributes. Then the principal component analysis is utilized to normalize the scaling matrix, and the normalization matrix is labeled as training sets. Moreover, the altered multi-dimensional Gaussian kernel density estimation is utilized for estimating the probability distribution of training set. Furthermore, diffusion map is used to discover and characterize the geometry and structure of dataset. In other words, nonlinear manifold based on the training set is constructed through diffusion map. Specifically, the first eigenvalue and corresponding eigenvector is related to the construction of diffusion basis and diffusion maps. Further, Itô-MCMC sampler is associated with dissipative Hamilton system driven by Wiener process, for which the initial condition is set to be training set, and prior probability is conceived as invariant measure. Störmer-Verlet scheme is used for solving the stochastic dissipative Hamilton equations. Finally, additional realizations of learning dataset are fulfilled through the inversion transformation. The result shows that random number generated from PLoM satisfies the requirements of industrial and high fidelity simulation. The 95% confidence interval of density is included in the range calibrated by Los Alamos National Laboratory. And the value of detonation velocity calibrated by Prof. Chengwei Sun [Sun C W, Wei Y Z, Zhou Z K 2000 Applied Detonation Physics (Beijing: National Defense Industry Press) p224] also falls into 95% confidence interval of detonation velocity generated by PLoM. It is also deduced from the learning set that density and detonation velocity satisfies the affine transformation. Furthermore, detonation pressure has nonlinear relationship with density. Tiny variation of density can lead to magnificent fluctuation of detonation pressure and detonation velocity. Detonation pressure has the largest discreetness in all the physical quantities through the comparison of variation coefficients of learning set, which coincides with the existing research results. The method used is universal enough and can be extended to other detonation systems.
2025, 74 (12): 120701.
doi: 10.7498/aps.74.20250249
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During flight operations, aircraft induces atmospheric disturbances in the surrounding environment through aerodynamic interactions between its geometric configuration and ambient air medium, resulting in spatially distinct density distribution characteristics that are significantly different from natural background scenario. Considering the positive correlation between atmospheric medium density and light scattering intensity, theoretical analysis shows that detecting the light scattering intensity signals in disturbed regions can map density distributions, thereby extracting the features of aircraft-induced atmospheric disturbance density fields. Based on the concept of long-range aircraft detection through atmospheric disturbance density field characterization, a novel remote sensing method for aircraft detection is proposed in this work. Specifically, a three-dimensional tomographic imaging detection mode for scattered light in an atmospheric disturbance region is designed, and a comprehensive simulation framework covering the entire process of disturbance optical signal generation, transmission, and response is constructed. The study accomplishes the following tasks: 1) the critical challenges in estimating the imaging modulation transfer function under short-exposure conditions subjected to laser pulse secondary scattering effects are resolved, and a photon scattering echo imaging simulation model for aircraft-induced disturbance density fields is established; 2) the scattering echo signal images from active light sources in disturbed density fields and the differential images obtained under disturbed background and non-disturbed background are simulated, with simulation results under varying system parameters analyzed systematically. The research demonstrates that this simulation model can be used to optimize detection system parameters, develop signal processing methods, and assess long-range detection capabilities, thus providing both theoretical foundations and technical support for advancing aircraft detection technologies based on density disturbance characteristics.
ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS
2025, 74 (12): 124101.
doi: 10.7498/aps.74.20241789
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2025, 74 (12): 124201.
doi: 10.7498/aps.74.20250373
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Real-time entropy source evaluated dual-parallel continuous variable quantum random number generator
2025, 74 (12): 124202.
doi: 10.7498/aps.74.20250333
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2025, 74 (12): 124203.
doi: 10.7498/aps.74.20250172
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Magnons, as quasiparticles arising from spin wave excitations in magnetic materials, have demonstrated significant application potential in quantum information technology, spintronics, and microwave engineering in recent years. The cavity magnon optomechanical system, serving as a key platform for investigating magneto-optical interactions, has advanced the exploration of nonlinear dynamical behaviors and the innovative design of quantum devices through strong coupling between magnons, photons, and phonons. However, traditional single-cavity systems face limitations in terms of tunability, long-range interactions, and nonlinear enhancement, making them insufficient for complex quantum control requirements. In recent years, dual-cavity systems have become a research hotspot due to their multidimensional control capabilities achieved through inter-cavity coupling, such as photon mode splitting and enhanced nonlinear Kerr effects. Meanwhile, semiconductor quantum dots, provide a novel pathway for regulating magnon dynamics due to their tunable nonlinear response characteristics. In this work, we construct a novel coupled quantum system by integrating quantum dots and a dual-cavity architecture, and investigate the bistable phenomena under both forward and backward driving field inputs. By comparing the third-order nonlinear equations governing magnon populations in the two scenarios, we derive the impedance matching condition. When this condition is satisfied, the magnon responses induced by forward driving field and backward driving field are identical. Conversely, under impedance mismatch, the magnon responses exhibit different behaviors. Specifically, when the impedance matching condition is violated, the dual-cavity magnon optomechanical system incorporating three-level quantum dot molecules exhibits a lower bistability threshold than its counterpart without quantum dots. This allows for a transition from low steady state to high steady state while reducing the driving field strength, thereby achieving switching functionality at lower input power. Furthermore, we establish a multiparameter cooperative control model, revealing a three-dimensional parameter space formed by tunneling coupling, cavity-quantum dot coupling, and inter-cavity coupling. By adjusting these coupling strengths, the bistability threshold and hysteresis loop width can be effectively controlled, thereby modulating the driving field intensity required for bistability. This system is expected to experimentally observe the magnonic bistability through the vector network analyzer-based detection of abrupt changes in transmission or absorption windows in reflection spectra. Such capabilities can advance data signal transmission, switching devices, and memory technologies, and has the potential to serve as components of large-scale quantum information processing units. Additionally, this research may find important applications in the field of magnetic spintronics.
2025, 74 (12): 124204.
doi: 10.7498/aps.74.20250153
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As a remarkable optical transformation enabling mutual conversion between Gaussian and Airy beams, the Airy transformation raises intriguing questions when applied to Airyprime beam—an advanced variant of conventional Airy beam. To answer these questions, numerical simulations and experimental verification are combined in this study. The results show two different operation regimes: when the Airy coefficient exceeds the negative transverse scale factor, the Airy-transformed optical field of Airyprime beam in any transverse direction becomes equivalent to the superposition of eccentric Airy beam and eccentric Airyprime beam; when the Airy coefficient equals the negative transverse scale factor, the transformed optical field equivalently corresponds to the sum of two displaced elegant Hermite-Gaussian beams. Analytical expressions for centroid and beam half width under both regimes are rigorously derived and validated experimentally by using Airy transformation of Airyprime beams to systematically measure the influences of Airy coefficientson intensity distribution, centroid displacement, and beam half width. This investigation provides a novel method for generating complex beam profiles while enhancing the potential application value of such beams in optical communication and beam-splitting technology.
2025, 74 (12): 124205.
doi: 10.7498/aps.74.20250123
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2025, 74 (12): 124301.
doi: 10.7498/aps.74.20250382
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2025, 74 (12): 124401.
doi: 10.7498/aps.74.20250347
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2025, 74 (12): 124701.
doi: 10.7498/aps.74.20250269
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The transition from laminar to turbulent flow is one of the main aerodynamic challenges in aircraft design and development. When the flight Mach number is sufficiently high, the aircraft surface experiences micropore effects and high-temperature gas thermochemical reactions. At present, boundary layer instability has become a more complex problem, and its mechanism is still unclear. In this study, a linear stability analysis method is developed which takes into consideration high-temperature chemical non-equilibrium process and surface micropore effect. For flight conditions at high altitude (H = 25 km) with Mach numbers 10, 15, and 20, the effects of micropore effects, chemical non-equilibrium effects, and their joint effect on flow stability are contrasted and investigated. The results show that the chemical non-equilibrium effect can contribute to the boundary layer's mode instability, while the micropore effect can restrain the second mode instability. The coexistence of the two often contributes to the instability of the second mode, because the former is heavier than the latter. The chemical non-equilibrium effect can reduce the frequency range corresponding to the second mode of pore effect inhibition, which results in the chemical non-equilibrium effect enhancing the inhibition effect of the micropore effect in the local low-frequency range and weakening its inhibition effect in the high-frequency range. This, in turn, causes a decrease in the corresponding N value variation by pore effect. Furthermore, when both effects are present, the micropore effect’s capacity to inhibit the second mode is not significantly affected by change in Mach number.
2025, 74 (12): 124702.
doi: 10.7498/aps.74.20250288
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2025, 74 (12): 124703.
doi: 10.7498/aps.74.20250289
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Friction resistance is the primary factor influencing the energy consumption and speed of underwater vehicles. Active air layer drag reduction is an active boundary layer control technique that reduces wall friction drag by injecting gas into the solid-liquid boundary layer. Compared with other drag reduction methods, which are often difficult to scale due to high costs and potential environmental concerns, this technology utilizes a simple auxiliary device. By employing inexpensive and environmentally friendly compressed air or combustion exhaust gases, it effectively lowers fluid resistance. Therefore, active drag reduction technology plays a crucial role in minimizing friction and enhancing overall performance. In this study, molecular dynamics simulations are used to construct a Couette flow shear model, with gas injected at the boundaries of a nanochannel. The flow characteristics and boundary drag reduction of Couette flow in a nanochannel is investigated in this work. The influence of gas injection on these characteristics is examined, along with the effects of surface wettability, shear velocity, and gas injection rate on boundary slip velocity and drag reduction. The results indicate that the gas adsorption on the solid surface in the form of discrete bubbles hinders liquid flowing and slipping near the wall, leading to the increase of drag. However, increasing surface hydrophobicity, shear rate, and gas injection rate facilitates the transverse spreading of bubbles, reduces flow obstruction, and enhances slip. Additionally, these factors promote the formation of a continuous gas layer from discrete bubbles, further improving drag reduction. Once the gas layer forms, shear stress decreases significantly, and slip velocity varies with surface wettability, shear velocity, and gas injection rate. These findings provide a theoretical foundation for developing the active gas layer drag reduction technology and optimizing the surface structures in ships and underwater vehicles.
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES
2025, 74 (12): 125201.
doi: 10.7498/aps.74.20250340
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The laser energy deposition coefficient, the electron thermal conduction coefficient, and the resistivity are three important physical quantities in plasma physics. For a multi-ion-component plasma, considering only the collisional interaction between electrons and ions, starting from the kinetic equation in the Fokker-Planck approximation, and using multi-timescale method, a unified derivation of the laser energy deposition coefficient, electron thermal conduction coefficient, and resistivity in the plasma is presented.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
2025, 74 (12): 126101.
doi: 10.7498/aps.74.20250286
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Magnetic high-entropy alloy (HEA) has certain application prospects in the fields of energy conversion, hysteresis motor, electromagnetic control mechanism and others. In this study, AlCoCrCuFeNi HEA is prepared by selective laser melting (SLM) with different process parameters, and the phase composition, microstructure, magnetic properties and micromechanical behavior are studied systematically. The results show that the SLMed alloy mainly consists of a BCC matrix phase with a small quantity of approximately spherical FCC precipitated nanophase. The nanohardness decreases with the increase of laser power and fluctuates in a certain range with the change of scanning speed, but the whole sample shows excellent micromechanical properties. Besides, it is found that the room-temperature nanoindentation creep deformation mechanism of AlCoCrCuFeNi HEAs is mainly controlled by dislocation motion, which is different from the results given by the traditional classical creep theory. Both of SLMed alloys exhibit typical semi-hard magnetic properties. The saturation magnetization is affected slightly by the SLM process parameters and remains at about 43 A·m2/kg because all samples have a similar quantity of ferromagnetic elements (Fe, Co and Ni). However, the coercivity increases from 1.72 to 2.71 kA/m with the increase of laser power (P), and decreases from 2.37 to 1.98 kA/m with the increase of scanning speed (v), which can be attributed to the different effects of porosity and internal stress on the pinning of domain walls under different process parameters (P and v). This work provides a theoretical basis and experimental direction for further studying the optimization of comprehensive magnetic properties and the room temperature creep mechanism of SLMed high-entropy alloy.
2025, 74 (12): 126301.
doi: 10.7498/aps.74.20241701
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The novel layered semiconductor material bismuth oxyselenide (Bi2O2Se) exhibits exceptional properties such as thickness-dependent bandgap, superior electron mobility, compatibility with various materials, and stability under ambient conditions. The zipper-type two-dimensional Bi2O2Se (Z-Bi2O2Se) is a newly proposed structure based on theoretical studies of material surface dissociation mechanisms. However, current understanding of this structure still mainly focuses on fundamental investigations of electronic properties such as band structures. Intrinsic point defects, which are inevitable during material synthesis and operational environments, significantly influence the physical characteristics of materials and ultimately dictate device performance. In this work, we conduct an in-depth exploration of intrinsic point defects in the material. Using first-principles calculations based on density functional theory (DFT) and non-equilibrium Green’s function (NEGF) methods, we systematically investigate the structural, electronic, and optoelectronic properties of vacancies, antisites, and adatom point defects in Z-Bi2O2Se. First, the formation energy calculations under different growth conditions reveal that o'vacancy, Se replaced by O, Se adsorption on “Bi'-Bi'-Se” and “Bi-Bi-Se” hollow sites are relatively easy to form. The density of states (DOS) and formation energy shows that o'vacancy, Se adsorption on “Bi'-Bi'-Se” and “Bi-Bi-Se” hollow sites tend to lose electrons and become positively charged. Their donor levels are located at 0.78 eV, 0.01 eV, and 0.07 eV above the valence band maximum (VBM), but well below the conduction band minimum (CBM), indicating deep-level n-type doping characteristics. Furthermore, devices based on monolayer Z-Bi2O2Se along the parallel (Z//) direction and perpendicular (Z⊥) direction of the “zipper” structure are constructed to investigate the influence of intrinsic point defects on optoelectronic performance. The results show that for pristine materials, the photocurrent of Z⊥-perfect in the visible and ultraviolet regions is two orders of magnitude smaller than that of Z//-perfect, demonstrating significant anisotropy. The introduction of point defects reduces system’s symmetry, leading to a remarkable enhancement of photocurrent in both devices in these spectral regions. Notably, in the Z⊥ direction, the point defects induce the photocurrent to increase by three orders of magnitude. However, the photocurrent remains relatively small compared with that in Z// direction, indicating persistent anisotropy. The influence of point defects on the extinction ratio depends on both defect types and photon energy. By selecting specific point defects under irradiation at targeted photon energy, the polarization sensitivity of devices can be effectively improved. These findings provide theoretical guidance for deepening the understanding of the electronic structure and optoelectronic properties of two-dimensional Z-Bi2O2Se.
2025, 74 (12): 126302.
doi: 10.7498/aps.74.20250251
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Two-dimensional transition metal borides (MBene), as emerging electrode materials for metal-ion batteries, exhibit various phase structures, including MB, M2B, and M2B2. However, current research on the M2B-phase system remains insufficient. This study focuses on the design of M2B-phase MBenes, pioneering the construction of two novel sulfur-functionalized materials, Zr2BS2 and Nb2BS2, while systematically elucidating their performance mechanisms as anode materials for lithium/sodium-ion batteries. Through first-principles calculations, both Zr2BS2 and Nb2BS2 demonstrate exceptional structural stability and superior electrochemical properties in sodium-ion battery applications. Specifically, they exhibit high theoretical specific capacities (624 mA·h/g and 616 mA·h/g) and remarkably low diffusion energy barriers for Na+ (0.131 eV and 0.088 eV). Moreover, their low open-circuit voltages (0.38 V and 0.21 V) effectively suppress dendrite growth, achieving an optimal balance between high capacity and operational safety. This work not only establishes a theoretical framework for MBene-based anode design but also provides critical insights into the correlation between surface functionalization, structural stability, and ion transport kinetics. These findings provide valuable guidance for developing other two-dimensional materials and non-layered systems, while contributing to mechanistic understanding of charge-discharge processes in transition metal dichalcogenide TMD-based lithium/sodium-ion batteries.
2025, 74 (12): 126401.
doi: 10.7498/aps.74.20250329
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Identifying key nodes in complex networks or evaluating the relative node importance with respect to others by using quantitative methods is a fundamental issue in network science. To address the limitations of existing approaches—namely the subjectivity in assigning weights to importance indicators and the insufficient integration of global and local structural information—this paper proposes an entropy-weighted multi-channel convolutional neural network framework (EMCNN). First, a parameter-free entropy-based weight allocation model is constructed to dynamically assign weights to multiple node importance indicators by computing their entropy values, thereby mitigating the subjectivity inherent in traditional parameter-setting methods and enhancing the objectivity of indicator fusion. Second, global and local structural features are decoupled and reconstructed into separate channels to form multi-channel feature maps, which significantly enhance the representational capacity of the network structure. Third, by leveraging the feature extraction capabilities of convolutional neural networks and the integration power of attention mechanisms, the framework extracts deep representations of nodes from the multi-channel feature maps, while emphasizing key structural information through attention-based weighting, thus enabling more accurate identification and characterization of node importance. To validate the effectiveness of the proposed method, extensive experiments are conducted on nine real-world networks by using the SIR spreading model, thereby assessing performance in terms of correlation, accuracy, and robustness. The Kendall correlation coefficient is used as the primary evaluation metric to measure the consistency between predicted node importance and actual spreading influence. Additionally, experiments are performed on three representative synthetic networks to further test the model’s generalizability. Experimental results demonstrate that EMCNN consistently and effectively evaluates node influence under varying transmission rates, and significantly outperforms mainstream algorithms in both correlation and accuracy. These findings highlight the powerful generalization ability and wide applicability of this method in the identification of key nodes in complex networks.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
2025, 74 (12): 127101.
doi: 10.7498/aps.74.20250107
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In order to further investigate and improve the mechanism of the interaction between pre-strain/pre-stress and hydrogen-adsorbed steel (Fe-C alloy) surface at the microstructural level, the first-principles calculations method is used to study the effects of uniaxial pre-strain on hydrogen adsorption and diffusion on C-doped Fe(110) surface. The influence of pre-strain on hydrogen adsorption and permeation is investigated from three aspects: surface atomic spatial configuration, binding energy (Eb), and electronic structure. The diffusion energy barriers for hydrogen permeation are calculated in both doped and undoped C atoms. The results demonstrate that doped C atoms induce octahedral lattice distortion in Fe crystals in different directions, creating “distortion” on the Fe(110) surface. Variations in distortion degree (DΔ) at different sites and their distances from C atom lead to inconsistent trends in adsorption configurations (H adsorption height d and unit surface area SΔ) and binding energy (Eb) under pre-strain. For adsorption configurations, d is coupled by ε and C atom effects: at the TFpure site (non-C-doped site ), d decreases as SΔ increases; under compression (ε decreases from 0% to –5%) at TF (C-doped site with C atom directly beneath the site), TFS (C-doped site located closer to the maximally distorted atom Fe135) and TFL sites (C-doped site located farther from the maximally distorted atom Fe135), d positively correlates with DΔ, while under tension (ε increases from 0% to 5%), d negatively correlates with SΔ. As ε increases from –5% to 5%, Eb peaks at TFpure then declines, whereas Eb at TF decreases initially before rising, and Eb at TFS/TFL monotonically increases. The analysis hows that Eb at TFS/TFL positively is correlated with the standard deviation (Sα) of the three internal angles in the triangular unit. The trend of diffusion energy barrier (E∆) is opposite to that of Eb. When H is adsorbed at C-doped sites, the adsorption configuration and binding energy calculations indicate that H tends to diffuse inward more readily. However, electronic structure analysis reveals repulsion between C and H atoms, accompanied by increased diffusion barriers compared with the scenarios in the undoped cases, causing H atoms to accumulate around C atoms rather than penetrate the bulk phase, thereby leading hydrogen atoms to embrittle. The calculations of adsorption configuration, binding energy, and diffusion barrier indicate that at doped sites (TFS site), increasing tensile strain can contribute to H diffusion into the steel microstructure, whereas compressive strain hinders it. This explains the engineering phenomenon where “higher carbon content exacerbates hydrogen embrittlement tendency under equivalent stress” on an atomic scale. This work elucidates the mechanism of H adsorption on pre-strained Fe-C alloy surfaces from an electronic structure perspective, providing theoretical ideas for studying hydrogen embrittlement.
2025, 74 (12): 127401.
doi: 10.7498/aps.74.20250410
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Earth-abundant molybdenum disulfide (MoS2), as a promising substrate for surface-enhanced Raman spectroscopy (SERS), has attracted considerable attention. Naturally occurring MoS2 primarily exists in the semiconducting 2H phase, but its SERS performance is limited because active sites are typically confined to its edges. Furthermore, the irregular agglomeration of MoS2 can lead to performance degradation, making natural semiconducting material unsuitable for practical applications. Therefore, enhancing the performance of MoS2 in the field of SERS is of great significance. Metal-organic frameworks (MOFs) are ideal materials for building efficient SERS substrates due to their tunable pore structures. Among various MOF materials, zeolitic imidazolate frameworks (ZIFs) have aroused significant interest due to their well-defined polyhedral structures, homogeneity, and small particle sizes. Therefore, in this study, MoS2/zeolitic imidazolate framework-67 (ZIF-67) heterostructures are prepared by the hydrothermal method as SERS substrates, which exhibits exceptionaly high sensitivity to rhodamine 6G with an enhancement factor of up to 6.68×106. Moreover, after SERS is exposed to air for four months, its performance remains almost unchanged, demonstrating high stability and reusability. To evaluate the actual detection ability of this substrate, bilirubin is selected as the analyte, which is a clinically relevant metabolic waste. Since both high and low concentrations of free bilirubin can lead to cardiovascular and cerebrovascular diseases, accurate monitoring of bilirubin levels is crucial for diagnosing bilirubin-induced disorders. Using the MoS2/ZIF-67 substrate, the label-free detection of bilirubin is achieved with a limit of detection as low as 10–10 mol/L. The outstanding performance of this substrate can be attributed to the vertically aligned MoS2 nanostructure, which exposes more active sites. Additionally, ZIF-67 provides a high specific surface area and abundant porous structures, providing numerous adsorption sites for target molecules. Furthermore, the internal charge transfer facilitates the formation of a highly conductive 1T phase, thereby improving electrical conductivity. This work provides valuable insights into the rational designing of noble-metal-free materials for highly sensitive SERS detection.
2025, 74 (12): 127501.
doi: 10.7498/aps.74.20250334
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Flexible ferroelectric materials possess considerable potentials for wearable electronics and bio-inspired devices, yet their mechano-electric coupling mechanisms under dynamic bending conditions remain incompletely understood. In his work, the effects of bending deformation on domain structures and macroscopic ferroelectric responses in (SrTiO3)10/(PbTiO3)10/(SrTiO3)10 flexible ferroelectric trilayer films are systematically investigated using phase-field simulations. By constructing computational models for upward-concave (U-shaped) and downward-concave (N-shaped) bending configurations, the strain distribution and its regulation mechanism on polarization patterns under different curvature radii are analyzed. The results reveal distinct strain gradients across bending modes: U-shaped bending induces compressive strain in the upper layer and tensile strain in the lower layer, generating a negative out-of-plane strain gradient. Conversely, N-shaped bending reverses this strain distribution. Such inhomogeneous strains drive significant polarization reconfiguration within the PTO layer. At a moderate curvature (large R), the system retains stable vortex-antivortex pairs. Reducing bending radius (smaller R) promotes divergent topological transitions—U-shaped bending facilitates vortex pair transformation into zigzag-like domains, while N-shaped bending drives vortex-to-out-of-plane c-domain evolution. Notably, bending-induced strain gradients impose transverse flexoelectric fields that markedly change trilayer hysteresis loops. U-shaped bending introduces a negative flexoelectric field, shifting loops rightward with maximum polarization (Pmax) decreasing. In contrast, N-shaped bending generates a positive field, enhancing Pmax via leftward loop shifting. The polarization switching analysis under electric field further demonstrates bending-mediated control of domain evolution pathway and reversal dynamics. These findings not only elucidate profound bending effects on flexible ferroelectrics’ domain architectures and functional properties but also provide theoretical guidance for designing strain-programmable ferroelectric memories, adaptive sensors, and neuromorphic electronics.
2025, 74 (12): 127701.
doi: 10.7498/aps.74.20250335
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2025, 74 (12): 127702.
doi: 10.7498/aps.74.20250277
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Simulating molecular structures and dynamic behaviors presents critical insights into the microscopic mechanisms governing variations in charge transport properties. In this work, molecular dynamics (MD) simulations integrated with the Compass II force field and molecular modeling (including geometry optimization, annealing, and dynamic equilibration) are conducted to systematically analyze intermolecular interaction energy, free volume distribution, electronic density of states (DOS), charge differential density, and trap energy levels. aiming to unravel the regulatory role of hydrogen bonds in the structural evolution and charge transport dynamics of polypropylene (PP)/polyvinylidene fluoride (PVDF) composite systems. A quantitative framework is further established to correlate hydrogen bond density with key material performance metrics, such as free volume fraction, bandgap energy, and trap energy depth, thereby elucidating the hydrogen bond-mediated modulation of molecular architecture and charge transport behavior in PP/PVDF composites. Simulation results reveal a pronounced dependence of hydrogen bond formation on maleic acid (MA) grafting content. When the mass fraction of MA is 36.22%, the number of hydrogen bonds reaches a maximum value of 20, the intermolecular interaction energy increases to 2171.63 kcal·mol–1, and the free volume fraction reaches a minimum value of 16.03%. At this point, the internal structure of the molecule is most compact. When the mass fraction of MA increases to 52.97%, the band gap of the composite material reaches a minimum value of 3.13 eV, and the depth of the trap energy levels also reaches a maximum value of 3.06 eV. Spatial charge differential density analysis demonstrates that the enhanced electron density is localized near hydrogen-bonded region, thus suppressing electron escape probability by over 40% compared with the scenario in the non-bonded domains. All of the findings highlight a dual mechanism: hydrogen bonds not only reconfigure the molecular topology but also reshape the localized charge distribution, directly suppressing the carrier mobility and changing the charge transport pathways. These findings also establish a robust structure-property relationship, showing that hydrogen bond engineering serves as a pivotal strategy to tailor dielectric performance in polymer composites. By optimizing hydrogen bond density, the trade-off between structural compactness and electronic confinement can be strategically balanced, thus enabling the designing of PP-based dielectrics with low carbon footprints and superior insulating properties. This mechanistic understanding provides actionable guidelines for advancing high-performance insulating materials in energy storage systems, aerospace components, and next-generation electrical devices, where precise control over charge transport is paramount.
COVER ARTICLE
2025, 74 (12): 127402.
doi: 10.7498/aps.74.20250391
Abstract +
CeRh2As2, as a recently discovered Ce-based 122-type heavy-fermion superconductor, has attracted much attention due to its non-Fermi-liquid behavior and two-phase superconductivity. The tetragonal crystal structure of CeRh2As2 maintains global centrosymmetry, which makes even-parity and odd-parity superconducting states different rather than mixed. The Ce site exhibits local inversion symmetry breaking, which results in staggered Rashba spin-orbit coupling. This may lead to the c axis field-induced transition between two superconducting phases and high critical field. Given the novel physics in CeRh2As2, including a possible quantum critical point and a spin-fluctuation-mediated superconducting pairing mechanism, the ultra-low-temperature electrical and thermal transport properties of CeRh2As2 under various magnetic fields are investigated in this work. The zero-field resistivity reveals a superconducting transition at the critical temperature Tc = 0.34 K. At a magnetic field of 1 T, a minimum resistivity appears near T0$ \approx $0.42 K, which may be due to partial gap opening caused by Fermi surface nesting, indicating that the system enters into a magnetically ordered state, which is not observed in zero field. In the temperature range from T0 to 2 K, the system exhibits non-Fermi-liquid behavior $ \rho\sim{{T}}^{0.44} $, indicating proximity to a quantum critical point. The superconducting transition is fully suppressed at 7 T, with resistivity recovering Fermi-liquid behavior at low temperature. No significant anomaly is observed in the zero-field thermal conductivity of CeRh2As2 near Tc. This absence of anomaly may be attributed to the high residual resistivity of the sample, and the reduction in carrier density during the superconducting transition and the T0 phase transition. It requires optimizing single crystal growth to reduce the effects of lattice defects or chemical disorder on thermal transport. Upon applying magnetic field, the thermal conductivity curve exhibits a small upward shift relative to its zero-field curve. At 0.15 K, thermal conductivity rises with the increase of magnetic field and is saturated at higher fields (above 5 T). In the normal state at 7 T, it is found that the electrical resistivity and thermal conductivity satisfy the Wiedemann-Franz law, indicating that both charge and heat transport are governed by the same quasiparticles, which is consistent with the Fermi-liquid behavior observed in resistivity under this field.
INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY
2025, 74 (12): 128101.
doi: 10.7498/aps.74.20250164
Abstract +
Strained silicon technology employing strain-relaxed SiGe virtual substrates has become pivotal factor in advancing group IV semiconductor electronics, photonic devices, silicon-based quantum computing architectures, and neuromorphic devices. Although existing approaches using Si/SiGe superlattice buffers and compositionally graded SiGe layers can produce high-quality SiGe virtual substrates, defects including threading dislocations and crosshatch patterns still limit further performance enhancement. This study demonstrates a method of fabricating fully elastically relaxed SiGe nanomembranes that effectively suppresses the formation of both threading dislocations and crosshatch patterns. The fabrication process comprises three key steps: 1) epitaxially growing Si/SiGe/Si heterostructures on silicon-on-insulator substrates via molecular beam epitaxy (MBE), 2) fabricating periodic pore arrays by using photolithography and reactive ion etching, and 3) selectively wet etching and subsequently transferring nanomembranes to Si(001) substrates. Subsequently, a Si/SiGe heterostructure is grown on the SiGe nanomembranes via MBE. The full elastic relaxation state of the SiGe nanomembranes and the fully strained state of the Si quantum well in the epitaxial Si/SiGe heterostructures are verified using Raman spectroscopy. Surface root-mean-square roughness value is 0.323 nm for the SiGe nanomembrane transferred to the silicon substrate and 0.118 nm for the epitaxial Si/SiGe heterostructure, which are demonstrated through atomic force microscopy measurements. Through electron channel contrast imaging, it is demonstrated that the Si/SiGe heterostructures grown on SiGe nanomembranes have uniform surface contrast and no detectable threading dislocations. Comparatively, the silicon substrate region exhibits high-density threading dislocations accompanied by stacking faults. Cross-sectional transmission electron microscope analysis shows atomically sharp and defect-free interfaces. This research lays a critical foundation for developing high-mobility two-dimensional electron gas systems and high-performance quantum bits.
2025, 74 (12): 128701.
doi: 10.7498/aps.74.20250171
Abstract +
2025, 74 (12): 128702.
doi: 10.7498/aps.74.20250504
Abstract +
Cold shock proteins (Csps) are a class of highly conserved nucleic acid-binding protein composed of 65−70 amino acids that form a compact β-barrel structure with five antiparallel β-strands. As nucleic acid-binding proteins, Csps play an important role in bacterial response to cold shock, yet their precise working mechanism is still unclear. As is well known, DNA hairpin undergoes folding-unfolding transitions under small constant forces. Magnetic tweezers technique has obvious advantages in this kind of research, especially its capacity for extended-duration constant-force measurements at pico-Newton force level, which makes it very suitable for characterizing the conformational transition dynamics of DNA hairpin at low forces of several pico-Newton. In this study, we first stretch DNA hairpin from its N- and C-termini by using magnetic tweezers. Then, we sequentially introduce Csp buffer solutions with increasing concentrations into the flow chamber and measure the folding and unfolding rates of the DNA hairpin at different Csp concentrations. It is found that within a certain concentration range, increasing Csp concentration can significantly reduce the DNA hairpin folding rate while keeping the unfolding rate almost unchanged. This behavior occurs because Csp only binds to single-stranded DNA (ssDNA), and interacts with the ssDNA region of the unfolded DNA hairpin, thereby hindering the folding process. As Csp does not interact with double-stranded DNA (dsDNA), the above-mentioned effect on the unfolding process is negligible. Furthermore, the critical force of DNA hairpin progressively decreases with the increase of Csp concentration, demonstrating that Csp effectively destabilizes the hairpin structure. When the Csp concentration reaches sufficiently high levels, the DNA hairpin’s unfolding rate increases considerably. This phenomenon may be caused by the rapid binding of Csp to newly exposed ssDNA regions of partially unfolded DNA hairpins, which prevents refolding and accelerates the unfolding pathway. In force-jump experiments using Csp-containing buffers, the binding preference of Csp for either ssDNA or dsDNA can be directly determined by analyzing whether the delayed response of DNA hairpin extension occurs. In force-increasing jump experiments, no extension delay is observed in the DNA hairpin unfolding process. In contrast, force-decreasing jump experiments shows significant extension delay in the folding process. These single-molecule measurements provide direct evidence that Csp only specifically binds to ssDNA, further demonstrating that its binding kinetics occur very rapidly. This study delves into the molecular mechanisms by which Csps maintain normal cellular functions in cold chock conditions.
2025, 74 (12): 128801.
doi: 10.7498/aps.74.20250184
Abstract +
Inorganic CsPbIBr2 perovskite features high phase stability and light absorption coefficient, making it suitable for the development of perovskite tandem cells or semi-transparent cells. High-quality CsPbIBr2 perovskite films are of crucial importance for fabricating efficient solar cells. However, compared with CsPbI3 and CsPbI2Br, the CsPbIBr2 precursor has poor crystallinity and low film coverage, which is prone to generating pinholes and defects. Therefore, serious charge recombination often occurs inside the devices. To solve this problem, p-aminobenzoic acid (PABA) is added to the CsPbIBr2 precursor to regulate its crystallization dynamics in this work. Electrostatic potential distribution of PABA shows that the electron-rich regions (negative charge regions) are mainly located near the C=O. Fourier transform infrared spectrum indicates the existence of coordination interaction between C=O and Pb²+ and the formation of hydrogen bonds between —NH2 and halide anions. Ultraviolet-visible absorption (UV-Vis) spectrum and X-ray diffraction (XRD) spectrum demonstrate that a new intermediate phase, PABA·Pb···Br(I), is formed between PABA molecules and the components of CsPbIBr2 precursor. The formation of this intermediate phase slows down the crystallization rate of the perovskite, regulates the grain growth, and enables the preparation of dense perovskite films. XRD, UV-Vis, space charge limited current, and linear sweep voltammetry are used to characterize the film quality. After the addition of PABA, the film quality of CsPbIBr2 perovskite is improved. Thus, the light absorption is enhanced. The defect density is reduced. And the conductivity is increased. The efficiency of the champion cell increases to 10.65% compared with that of the control cell (8.76%). Further, dark current-voltage curves, Mott-Schottky curves, electrochemical impedance spectra, and photoluminescence spectra are utilized to analyze the reasons for the improved photovoltaic performance. After the addition of PABA, the CsPbIBr2 device exhibits reduced leakage current, enhanced built-in electric field, suppressed charge recombination, and improved charge extraction at the interface. In addition to the enhancement in photovoltaic efficiency, the PABA-regulated perovskite cells also exhibit high stability. After being stored in air for 1500 h, the average efficiency of the unencapsulated cells remains 80% of the initial value.
GEOPHYSICS, ASTRONOMY, AND ASTROPHYSICS
2025, 74 (12): 129401.
doi: 10.7498/aps.74.20250183
Abstract +
In the context of the development of aerospace integration, the near-space aircraft is facing the challenge of autonomous navigation under the satellite denial conditions. Pulsar navigation is a promising solution, and its applicability depends on the transmission characteristics of X-rays in near-space. Firstly, in this paper the interactions between X-rays and charged ions, free electrons and other substances in the ionosphere are analyzed, and the mass attenuation coefficients of reflection, scattering and absorption to X-rays with energy of 1–100 keV are presented. Then, based on the NRLMSIS 2.1 model and IRI-2020 model, a stratified model for X-ray transmission in nearspace is established, and the transmission efficiency and flux acquisition method for 1–30 keV X-rays in 60–100 km are obtained. Finally, the variations in transmission efficiency under the conditions of different seasons, latitudes and days and nights are analyzed, and the distribution characteristics of transmission efficiency are described. Analysis results are shown below. 1) Photoelectric absorption plays a dominant role, while coherent scattering and incoherent scattering have relatively minor influence and the reflection effect is extremely weak and negligible for X-rays applicable to pulsar navigation. 2) The transmission efficiency exhibits a significant positive correlation with X-ray energy and altitude, and it usually exceeds 80% when the X-ray energy exceeds 10 keV. 3) The transmission efficiency exhibits distinct annual variation characteristics in the Arctic region and Antarctic region and subtle semi-annual variation characteristics in the equatorial region. It peaks in the winter hemisphere and reaches a minimum in the summer hemisphere, with the amplitude of its fluctuations in polar regions far exceeding that in the equatorial region. Additionally it also shows the periodic daily variations with daytime decreasing and nighttime increasing, and the amplitude of diurnal fluctuations being no more than 0.82%. The results indicate that the transmission efficiency peaks in the early morning of the Antarctic winter for 10 keV X-rays at 75 km. Taking Antarctic China Zhongshan Station for example, it can reach up to 93.57%, which means a 9.61% increase over the summer minimum of 83.96%. This study provides crucial data for supporting the applications of X-ray pulsar navigation in nearspace.
