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We propose a quantum tomography (QT) approach to retrieve the temporally evolving reduced density matrix in electronic state basis, where the populations and coherence between the ground state and excited state are reconstructed from the ultrafast electron diffraction signal. In order to showcase the capability of the proposed QT approach, we simulate the nuclear wavepacket dynamics and ultrafast electron diffraction of photoexcited pyrrole molecules using the ab initio quantum chemical CASSCF method. From the simulated time-resolved diffraction data, we retrieve the evolving density matrix in a crude diabatic representation basis and reveal the symmetry of the excited pyrrole wavepacket. Our QT approach opens the route to make a quantum version of "molecular movie" that covers the electronic degree of freedom and equips ultrafast electron diffraction with the power to reveal the coherence between electronic states, relaxation, and dynamics of population transfer. [ABSTRACT FROM AUTHOR]

Mixed thorium/uranium dioxide, (Th,U)O2, is under consideration for advanced nuclear fuel applications. Investigating the point defect structure and energy in this oxide is important for predicting its behavior as fuel. In this work, we use first-principles calculations based on the generalized gradient approximation (GGA)+Hubbard U approach to investigate the internal energy and entropy of the formation of point defects in Th1−xUxO2 at various compositions below x ≤ 0.5. Point defects including O vacancies, O interstitials, Th vacancies, Th interstitials, U vacancies, and U interstitials have all been considered with their charges ranging from neutral to the maximum nominal values. The observed trends have been explained in terms of electronic density of states. The valence band maxima of crystals that contain defects play a crucial role and exhibit variations depending on the U content and the applied charge. The temperature dependence of internal energy and entropy of formation of defects have also been examined. The internal energy of formation of defects was found to exhibit slowly varying or constant values with respect to changes in the U content, except at low values of x and low temperatures. The entropy of formation of defects was observed to decrease with increasing U content. It was additionally observed that the entropy of formation of vacancies increases with temperature, while that of interstitials decreases. This investigation further revealed that at 0 K, the cation vacancies and anion interstitials become increasingly favorable with increasing U content, while cation interstitials and anion vacancies become less favorable. [ABSTRACT FROM AUTHOR]

We report on a strategy to indirectly read out the spectrum of an electronic spin via polarization transfer to nuclear spins in its local environment. The nuclear spins are far more abundant and have longer lifetimes, allowing for repeated polarization accumulation in them. Subsequent nuclear interrogation can reveal information about the electronic spectral density of states. We experimentally demonstrate the method by reading out the ESR spectrum of nitrogen vacancy center electrons in diamond via readout of lattice 13C nuclei. Spin-lock control on the 13C nuclei yields a significantly enhanced signal-to-noise ratio for the nuclear readout. Spectrally mapped readout presents operational advantages in being background-free and immune to crystal orientation and optical scattering. We harness these advantages to demonstrate applications in underwater magnetometry. The physical basis for the "one-to-many" spectral map is itself intriguing. To uncover its origin, we develop a theoretical model that maps the system dynamics, involving traversal of a cascaded structure of Landau–Zener anti-crossings, to the operation of a tilted "Galton board." This work points to new opportunities for "ESR-via-NMR" in dilute electronic systems and in hybrid electron–nuclear quantum memories and sensors. [ABSTRACT FROM AUTHOR]

We present the chemical bonding and electronic properties of liquid methane at temperatures from 2000 to 4000 K and high densities of up to 3.0 g/cm3, calculated using ab initio molecular dynamics simulations in combination with the Mulliken population analysis. Bond-overlap populations and pair distribution functions are studied to investigate the evolution of electron delocalization accompanying atomic structure change as the density is increased. In addition, we also investigated the bandgap energy, electronic density of states, and spatial distribution of electron density. We observed that molecular hydrogen and C‒C bonds are formed after methane dissociates, and then the system undergoes a nonmetal–metal transition coinciding with hydrogen being transformed from the molecular to the atomic state. The C‒C bonds in the system retain covalent character, even at the highest density of 3.0 g/cm3. [ABSTRACT FROM AUTHOR]

Because of their quantum confinement effects and adjustable features, semiconductor nanoparticles have attracted a lot of attention for their various uses in optoelectronic devices. This study investigates how size and shape variations affect the optoelectronic properties of semiconductor nanoparticles InX (X = As, Sb, and P). Using unified thermodynamics modeling, it explores the effects of these nanoparticles' diameters on their electronic band structures, optical properties, and charge carrier dynamics. The inquiry focuses on InX nanoparticles with different sizes and nanostructure morphologies. By examining electronic band structures, the density of states, and optical absorption spectra, the size-dependent quantum confinement processes that govern the optical band gap transitions and excitonic behaviors in these semiconductor nanoparticles were made clear. Also, the influence of the shape of the nanoparticles on carrier mobility and electronic band alignment is investigated, offering insights into the possibility of controlling the morphology to customize optoelectronic capabilities. This theoretical analysis indicates that altering the optoelectronic properties of InX semiconductor nanoparticles is mostly dependent on their size and shape. Smaller nanoparticles show stronger quantum size effects, which lead to improved exciton confinement and blue shifts in the optical absorption spectra. Shape-dependent differences in the density of states and electronic band structures indicate the impact of morphology on the dynamics and recombination of charge carriers in the nanoparticles. In conclusion, this work provides important insights for the design and optimization of semiconductor nanomaterials for photovoltaic, sensing, and light-emitting applications by thoroughly examining the impact of size and shape on the optoelectronic properties of InX semiconductor nanoparticles. [ABSTRACT FROM AUTHOR]

Aromatic amines are important commercial chemicals, but their carcinogenicity poses a threat to humans and other organisms, making their rapid quantitative detection increasingly urgent. Here, amorphous MoO3 (a‐MoO3) monolayers with localized surface plasmon resonance (LSPR) effect in the visible region are designed for the trace detection of carcinogenic aromatic amine molecules. The hot‐electron fast decay component of a‐MoO3 decreases from 301 fs to 150 fs after absorption with methyl orange (MO) molecules, indicating the plasmon‐induced hot‐electron transfer (PIHET) process from a‐MoO3 to MO. Therefore, a‐MoO3 monolayers present high SERS performance due to the synergistic effect of electromagnetic enhancement (EM) and PIHET, proposing the EM‐PIHET synergistic mechanism in a‐MoO3. In addition, a‐MoO3 possesses higher electron delocalization and electronic state density than crystal MoO3 (c‐MoO3), which is conducive to the PIHET. The limit of detection (LOD) for o‐aminoazotoluene (o‐AAT) is 10−9 M with good uniformity, acid resistance, and thermal stability. In this work, trace detection and identification of various carcinogenic aromatic amines based on a‐MoO3 monolayers is realized, which is of great significance for reducing cancer infection rates. [ABSTRACT FROM AUTHOR]

Resonant inelastic x-ray scattering (RIXS) is a widely used spectroscopic technique, providing access to the electronic structure and dynamics of atoms, molecules, and solids. However, RIXS requires a narrow bandwidth x-ray probe to achieve high spectral resolution. The challenges in delivering an energetic monochromated beam from an x-ray free electron laser (XFEL) thus limit its use in few-shot experiments, including for the study of high energy density systems. Here we demonstrate that by correlating the measurements of the self-amplified spontaneous emission (SASE) spectrum of an XFEL with the RIXS signal, using a dynamic kernel deconvolution with a neural surrogate, we can achieve electronic structure resolutions substantially higher than those normally afforded by the bandwidth of the incoming x-ray beam. We further show how this technique allows us to discriminate between the valence structures of Fe and Fe2O3, and provides access to temperature measurements as well as M-shell binding energies estimates in warm-dense Fe compounds. The authors combine differentiable physics modelling and neural networks to extract high-resolution electronic density of states of warm dense materials from resonant inelastic x-ray scattering spectra. With this approach, they identify distinctive features in the valence structures of warm dense Fe and Fe2O3, also estimating their temperature and M-shell binding energies. [ABSTRACT FROM AUTHOR]

Regulating the crystal morphology of low aspect ratio, short columnar α‐hemihydrate gypsum (α‐HH) is crucial due to its distinctive physical and chemical properties, which make it widely applicable. In this work, succinic acid, malic acid, and maleic acid were selected as the research objects, among which the number and spacing of carboxyl groups were the same, while the auxiliary functional groups were different. The adsorption energy, Mulliken charge population, electronic state density, and charge density difference of the three organic acids on the surfaces of α‐HH were calculated by well‐defined ab initio calculations. The results showed that the synergistic effect of ‐COOH groups is necessary for the effective crystallization of α‐HH. Organic acids interact with the Ca atoms on the crystal surface, as evidenced by their preferential adsorption on the top surface of α‐HH crystals (002). This interaction occurs through a double‐dentate chelation between the carboxyl oxygen atoms at both ends of the organic acid and the Ca atoms on the crystal surface, resulting in the formation of a six‐membered cyclic organic acid calcium complex. This complex hinders ion diffusion and the stacking of crystal surfaces, leading to a decrease in the growth rate along the c‐axis and promoting more extensive crystal development and larger crystal sizes. The work provides insight into the preparation of short prismatic α‐HH using organic acid crystallizing agents. [ABSTRACT FROM AUTHOR]

This brief review covers the thermoelectric properties of one-dimensional materials, such as nanowires and nanotubes. The highly localised peaks of the electronic density of states near the Fermi levels of these nanostructured materials improve the Seebeck coefficient. Moreover, quantum confinement leads to discrete energy levels and a modified density of states, potentially enhancing electrical conductivity. These electronic effects, coupled with the dominance of Umklapp phonon scattering, which reduces thermal conductivity in one-dimensional materials, can achieve unprecedented thermoelectric efficiency not seen in two-dimensional or bulk materials. Notable advancements include carbon and silicon nanotubes and Bi3Te2, Bi, ZnO, SiC, and Si1−xGex nanowires with significantly reduced thermal conductivity and increased ZT. In all these nanowires and nanotubes, efficiency is explored as a function of the diameter. Among these nanomaterials, carbon nanotubes offer mechanical flexibility and improved thermoelectric performance. Although carbon nanotubes theoretically have high thermal conductivity, the improvement of their Seebeck coefficient due to their low-dimensional structure can compensate for it. Regarding flexibility, economic criteria, ease of fabrication, and weight, carbon nanotubes could be a promising candidate for thermoelectric power generation. [ABSTRACT FROM AUTHOR]

Thermoelectric cooling materials based on Bi2Te3 have a long history of unsurpassed performance near room temperature. Recently, research into price‐competitive Mg3(Bi, Sb)2‐based materials are focused on replacing traditional cooling materials. Here, the thermoelectric properties of Mg3.2Bi1.998−xSbxTe0.002Cu0.005 (x = 0.0, 0.1, 0.2, 0.3, 0.4, and 0.5) polycrystalline compounds are investigated. In all temperature regions, electrical resistivity and Seebeck coefficient are increased with Sb concentration. The electronic transport properties of Sb‐alloyed compounds are maximized by synergistically combined band engineering approaches such as band structure change caused by lattice strain, increased electronic density of states, and chemical potential shift, leading to exceptionally high‐power factor values of over 3.0 mW m−1 K−2 at room temperature. Furthermore, with increasing Sb content, thermal conductivity values are systematically reduced due to the promotion of alloy scattering of phonons and suppression of the bipolar contribution. Consequently, these multiple approaches significantly enhance thermoelectric performance, resulting in an enhancement of thermoelectric figure‐of‐merit zT above 1.1 at 348–423 K. Additionally, a zTavg of 1.1 is recorded at 300–450 K, making it an unrivaled value among the reported n‐type Mg3Bi2‐based thermoelectric materials. Overall, this work demonstrates that Mg3Bi2‐based materials are more promising for thermoelectric cooling applications compared to Bi2Te3‐based materials. [ABSTRACT FROM AUTHOR]

Based on the first principles, the structural stability, mechanical characteristics, electronic structure, and thermodynamic properties of AlCu2M (M = Ti, Cr, Zr, Sc, Hf, Mn, Pa, Lu, Pm) are investigated. The calculated results indicate that the AlCu2Pa crystal structure is more stable and that AlCu2Pa should be easier to form. All of the AlCu2M compounds have structural stability in the ground state. Elastic constants are used to characterize the mechanical stability and elastic modulus, while the B/G values and Poisson ratio demonstrate the brittleness and ductility of AlCu2M compounds. It is demonstrated that all computed AlCu2M compounds are ductile and mechanically stable, with AlCu2Hf having the highest bulk modulus and AlCu2Mn having the highest Young's modulus. AlCu2Mn has the highest intrinsic hardness among AlCu2M compounds, according to calculations of their intrinsic hardness. The electronic densities of states are discussed in detail; it was discovered that all AlCu2M compounds form Al-Cu and Al-M covalent bonds. Additionally, we observe that the Debye temperature and minimum thermal conductivity of AlCu2Mn and AlCu2Sc are both larger than those of others, indicating stronger chemical bonds and higher thermal conductivities, which is consistent with the elastic modulus results. [ABSTRACT FROM AUTHOR]

In this study, the electronic density of states (DOSs) calculated with density functional theory (DFT) were analyzed by the machine‐learning techniques. More than 400 pure metal and bimetallic alloy systems were calculated with DFT, and obtained the surface DOSs and the CH3 adsorption energy (Ead). By fitting the Gaussian functions to the DOS, multiple descriptors, such as the Gaussian peak positions, heights, and widths were extracted. Several regression methods, such as the least absolute shrinkage of selection operator (LASSO), random‐forest, gradient‐boosting, and extra‐tree were used to find the relationship between these descriptors and the Ead. The results show that the energy position of the peaks in the d‐projected DOS is the most important descriptor, in agreement with the previously known d‐band center theory. It was also shown that the peak position in d‐projected DOS improves the regression model in addition to the d‐band center, since it reduces the regression error. [ABSTRACT FROM AUTHOR]

Ultrafast control over the magnetic orientation of matter represents a vital element of potential future spin-based electronics ("spintronics"). While physical mechanisms underpinning spin switching are established for picosecond time scales, we here present a physical route to magnetization toggle control, i.e., multiple switching events, at <100 femtoseconds. A minority spin current injected into a ferromagnet is shown to generate rapid depopulation of the minority channel below the ground-state Fermi level, creating a minority "spin vacuum" that then drives rapid charge redistribution from the majority channel and spin switching. We demonstrate that this mechanism reproduces many of the features of recent subpicosecond switching of ferromagnetic Co/Pt multilayers and provide simple practical rules for the design of materials via tailoring the electronic density of states to optimize spin vacuum control over magnetic order. [ABSTRACT FROM AUTHOR]

The optical properties of bulk AuCu3-type ordered superconducting binary compounds ScGa3 and LuGa3 have been experimentally investigated for the first time in the wide spectral range and explained in terms of the band structure. First-principles calculations of electronic densities of states and optical conductivities are performed within the framework of LSDA+U method using the LMTO-ASA software package. The measured dielectric functions spectra for both materials exhibit a strong absorption region above ∼ 1 eV, which are in a reasonable agreement with the calculated metal-like energy structures of compounds. Features of quantum light absorption are discussed on the basis of a comparative analysis of experimental and theoretical spectra of interband optical conductivity. Plasma and relaxation frequencies of conduction electrons are determined. [ABSTRACT FROM AUTHOR]

The optical properties of bulk AuCu3-type ordered superconducting binary compounds ScGa3 and LuGa3 have been experimentally investigated for the first time in the wide spectral range and explained in terms of the band structure. First-principles calculations of electronic densities of states and optical conductivities are performed within the framework of LSDA+U method using the LMTO-ASA software package. The measured dielectric functions spectra for both materials exhibit a strong absorption region above ∼ 1 eV, which are in a reasonable agreement with the calculated metal-like energy structures of compounds. Features of quantum light absorption are discussed on the basis of a comparative analysis of experimental and theoretical spectra of interband optical conductivity. Plasma and relaxation frequencies of conduction electrons are determined. [ABSTRACT FROM AUTHOR]

CuCrZr alloy is widely used in vacuum circuit breaker contact materials and high‐speed railroad contact wires, etc. The study of the effect of different Cr and Zr contents on the performance of CuCrZr alloy is of great significance for the improvement of circuit breaker's breaking capacity, as well as the load and structural stability under harsh working conditions. In this paper, the mechanical properties, electronic density of states and thermodynamic properties of CuCrZr solid solution alloys randomly doped by different concentrations of Cr and Zr are comparatively analyzed using first‐principles calculations based on density functional theory. The results show that the alloys with different doping compositions have strong mechanical stability, electrical conductivity, and thermomechanical stability, and the reduction of the Cr/Zr doping concentration ratio can improve the toughness and ductility of the alloys, and the solid solution alloy with the composition of CuCr0.06Zr0.19 has the best machinability. The doping of Cr and Zr can improve the thermal stability of the alloy, Cr and Zr can be used as high‐temperature toughening elements for Cu. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

We investigated the impact of annealing on the structural characteristics and superconducting critical temperature ( T c ) of the eutectic high-entropy alloy (HEA) superconductor NbScTiZr. The HEA manifests an eutectic microstructure composed of body-centered cubic (bcc) and hexagonal close-packed phases. Both the lattice parameters of the bcc phase and grain size of the eutectic structure exhibited pronounced sensitivity to variations in annealing temperature. The observed dependence of the lattice parameter on annealing temperature supports the possibility that lattice strain occurs at lower annealing temperatures. The as-cast sample demonstrated superconductivity at T c of 7.9 K, which increased to 9 K after annealing at 800 ∘ C. However, when subjected to annealing at 1000 ∘ C, T c diminishes to 8.7 K. The annealing temperature dependence of T c cannot be comprehensively elucidated based solely on the electronic density of states at the Fermi level. It is plausible that the lattice strain may influence the annealing temperature dependence of T c . Our results for the critical current density J c reveal that the self-field J c of the as-cast NbScTiZr at 2 K exceeds 10 6 A/cm 2 . [ABSTRACT FROM AUTHOR]

We report a Kohn–Sham density functional theory calculation of a system with more than 200 000 atoms and 800 000 electrons using a real-space high-order finite-difference method to investigate the electronic structure of large spherical silicon nanoclusters. Our system of choice was a 20 nm large spherical nanocluster with 202 617 silicon atoms and 13 836 hydrogen atoms used to passivate the dangling surface bonds. To speed up the convergence of the eigenspace, we utilized Chebyshev-filtered subspace iteration, and for sparse matrix–vector multiplications, we used blockwise Hilbert space-filling curves, implemented in the PARSEC code. For this calculation, we also replaced our orthonormalization + Rayleigh–Ritz step with a generalized eigenvalue problem step. We utilized all of the 8192 nodes (458 752 processors) on the Frontera machine at the Texas Advanced Computing Center. We achieved two Chebyshev-filtered subspace iterations, yielding a good approximation of the electronic density of states. Our work pushes the limits on the capabilities of the current electronic structure solvers to nearly 106 electrons and demonstrates the potential of the real-space approach to efficiently parallelize large calculations on modern high-performance computing platforms. [ABSTRACT FROM AUTHOR]

We investigate the source of error in the Thomas–Fermi–von Weizsäcker (TFW) density functional relative to Kohn–Sham density functional theory (DFT). In particular, through numerical studies on a range of materials, for a variety of crystal structures subject to strain and atomic displacements, we find that while the ground state electron density in TFW orbital-free DFT is close to the Kohn–Sham density, the corresponding energy deviates significantly from the Kohn–Sham value. We show that these differences are a consequence of the poor representation of the linear response within the TFW approximation for the electronic kinetic energy, confirming conjectures in the literature. In so doing, we find that the energy computed from a non-self-consistent Kohn–Sham calculation using the TFW electronic ground state density is in very good agreement with that obtained from the fully self-consistent Kohn–Sham solution. [ABSTRACT FROM AUTHOR]

We report the in-plane electron transport in the MXenes (i.e., within the MXene layers) as a function of composition using the density-functional tight-binding method, in conjunction with the non-equilibrium Green's functions technique. Our study reveals that all MXene compositions have a linear relationship between current and voltage at lower potentials, indicating their metallic character. However, the magnitude of the current at a given voltage (conductivity) has different trends among different compositions. For example, MXenes without any surface terminations (Ti3C2) exhibit higher conductivity compared to MXenes with surface functionalization. Among the MXenes with –O and –OH termination, those with –O surface termination have lower conductivity than the ones with –OH surface terminations. Interestingly, conductivity changes with the ratio of –O and –OH on the MXene surface. Our calculated I–V curves and their conductivities correlate well with transmission functions and the electronic density of states around the Fermi level. The surface composition-dependent conductivity of the MXenes provides a path to tune the in-plane conductivity for enhanced pseudocapacitive performance. [ABSTRACT FROM AUTHOR]

In Born–Oppenheimer molecular dynamics (BOMD) simulations based on the density functional theory (DFT), the potential energy and the interatomic forces are calculated from an electronic ground state density that is determined by an iterative self-consistent field optimization procedure, which, in practice, never is fully converged. The calculated energies and forces are, therefore, only approximate, which may lead to an unphysical energy drift and instabilities. Here, we discuss an alternative shadow BOMD approach that is based on backward error analysis. Instead of calculating approximate solutions for an underlying exact regular Born–Oppenheimer potential, we do the opposite. Instead, we calculate the exact electron density, energies, and forces, but for an underlying approximate shadow Born–Oppenheimer potential energy surface. In this way, the calculated forces are conservative with respect to the approximate shadow potential and generate accurate molecular trajectories with long-term energy stabilities. We show how such shadow Born–Oppenheimer potentials can be constructed at different levels of accuracy as a function of the integration time step, δt, from the constrained minimization of a sequence of systematically improvable, but approximate, shadow energy density functionals. For each energy functional, there is a corresponding ground state Born–Oppenheimer potential. These pairs of shadow energy functionals and potentials are higher-level generalizations of the original "zeroth-level" shadow energy functionals and potentials used in extended Lagrangian BOMD [Niklasson, Eur. Phys. J. B 94, 164 (2021)]. The proposed shadow energy functionals and potentials are useful only within this extended dynamical framework, where also the electronic degrees of freedom are propagated as dynamical field variables together with the atomic positions and velocities. The theory is quite general and can be applied to MD simulations using approximate DFT, Hartree–Fock, or semi-empirical methods, as well as to coarse-grained flexible charge models. [ABSTRACT FROM AUTHOR]

First-principles simulations are conducted to explore the structural stability, electronic properties, and optical responses of pristine and boron- or nitrogen-doped monolayers graphene. The computed electronic density of states revealed that the substitutional doping of boron impurity atoms on monolayer graphene (MLG) shifts the Dirac point upward, although the substitution of nitrogen impurity atoms in graphene pushes the Dirac point downward the Fermi level. This could exhibit that upon the doping of MLG with boron or nitrogen, respectively, p-type or n-type semimetal is acquired. The overall optical spectral properties of the substituted graphene with boron or nitrogen atoms are simulated and compared with the optical spectra results of pure graphene. The optical features of pristine and doped MLG are determined by taking the interband and intra-band transitions into account ranging from the far-infrared to the ultraviolet regime of the electromagnetic radiation. A remarkable red shift in the optical spectra of the doped MLG towards the visible regime of radiation is established. An enhanced reflectivity illustrated that concentration-dependent optical properties of boron and nitrogen-doped MLG happen at lower electromagnetic radiation regimes. In addition, we explored the thermoelectric behaviors of the pristine/doped graphene monolayers with 4 × 4 supercells. We found a significant improvement in the electrical conductivity of graphene when doped with boron or nitrogen impurities. However, an increase in the electrical conductivity has textured a decrease in the Seebeck coefficients. Improvement in the electrical conductivity is attributed to an interesting effect on the graphene monolayers' power factor (PF). These findings indicate a positive impact of the dopants on the thermoelectric properties of graphene monolayers and reveal that they are potential materials for thermoelectric applications and nanodevices. [ABSTRACT FROM AUTHOR]

A hybrid atomistic-continuum method can model the microstructure evolution of metals subjected to laser irradiation. This method combines classical molecular dynamics (MD) simulations with the two-temperature model (TTM) to account for the laser energy absorption and heat diffusion behavior. Accurate prediction of the temperature evolution in the combined MD-TTM method requires reliable accuracy in electron heat capacity, electron thermal conductivity, and electron–phonon coupling factor across the temperatures generated. This study uses the electronic density of states (DOS) obtained from first-principle calculations. The calculated electron temperature-dependent parameters are used in MD-TTM simulations to study the laser metal interactions in FCC and BCC metals and the phenomenon of laser shock loading and melting. This study uses FCC Al and BCC Ta as model systems to demonstrate this capability. When subjected to short pulsed laser shocks, the dynamic failure behavior predicted using temperature-dependent parameters is compared with the experimentally reported single-crystal and nanocrystalline Al and Ta systems. The MD-TTM simulations also investigate laser ablation and melting behavior of Ta to compare with the ablation threshold reported experimentally. This manuscript demonstrates that integrating the temperature-dependent parameters into MD-TTM simulations leads to the accurate modeling of the laser–metal interaction and allows the prediction of the kinetics of the solid–liquid interface. [ABSTRACT FROM AUTHOR]

Doping or partially substituting WC with metals, e.g., Mo and Cr, can lower its density while keeping the strength of the modified carbides similar to that of WC, making them attractive as the reinforcement for hardfacing overlays and tool steels, since they can be distributed homogeneously in the metal matrix. However, it is unclear if the doped WC has desirable interfacial bonding with the matrix, e.g., iron. In this study, we investigated the interfacial bonding of Mo- and Cr-doped WC, compared to that of mono-WC, with austenite and ferrite irons via first-principles calculations. (11 2 ¯ 0) C a r b i d e / / (110) F e , (10 1 ¯ 0) C a r b i d e / / (100) F e , and (0001) C a r b i d e / / (100) F e interfaces for both ferrite and austenite with the lowest interfacial mismatch were investigated. Characteristics of the formed interfacial bonds were studied based on the electron localization function, electronic density of states, bond order, and net charge. It was demonstrated that the Mo and Cr-doped WC carbides, (W4−x, M)C4, show comparable or higher adhesive work with iron, compared to that of mono-WC with iron. The metal-substituted or doped W4C4 carbides are promising replacements of heavier WC for tool steels and ferrous hardfacing overlays. [ABSTRACT FROM AUTHOR]

Despite advances in mixed tin‐lead (Sn‐Pb) perovskite‐based solar cells, achieving both high‐efficiency and long‐term device stability remains a major challenge. Current device deficiencies stem partly from inefficient carrier transport, originating from defects and improper band energy alignment among the device's interfaces. Developing multifunctional interlayer materials simultaneously addressing the above concerns poses an excellent strategy. Herein, through molecular and crystal engineering, an amine‐functionalized C60 mono‐adduct derivative (C60‐2NH3 = bis(2‐aminoethyl) malonate‐C60) is utilized for the synthesis of the first crystalline fullerene‐based 2D metal halide semiconductor, namely (C60‐2NH3)Pb2I6. Single crystal XRD studies elucidated the structure of the new material, while DFT calculations highlighted the strong contribution of C60‐2NH3 to the electronic density of states of the conduction band of (C60‐2NH3)Pb2I6. Utilization of C60‐2NH3 as an interlayer between a FA0.6MA0.4Pb0.7Sn0.3I3 perovskite and a C60 layer offered superior band energy alignment, reduced nonradiative recombination, and enhanced carrier mobility. The corresponding perovskite solar cell (PSC) device achieved a power conversion efficiency (PCE) value of 21.64%, maintaining 90% of its initial efficiency, after being stored under a N2 atmosphere for 2400 h. This work sets the foundation for developing a new family of functional materials, namely Fullerene Metal Halide Semiconductors, targeting applications from photovoltaics to catalysis, transistors, and supercapacitors. [ABSTRACT FROM AUTHOR]

Metal–support interaction plays a critical role in determining the eventual catalytic activity of metals loaded on supporting substrates. This interaction can sometimes cause a significant drop in the metallic property of the loaded metal and, hence, a drop in catalytic activity in the reactions, especially in those for which low charge carrier transfer resistance is a necessary parameter. Therefore, there should be a case-by-case experimental or theoretical (or both) in-depth investigation to understand the role of support on each metal. Here, onto a layered porous carbon nitride (g-CN), we grew single crystalline Pt nanodisks (Pt@g-CN) with a lateral average size of 21 nm, followed by various characterisations such as electron microscopy techniques, and the measurement of electrocatalytic activity in the O2 reduction reaction (ORR). We found that intercalating Pt nanodisks in the g-CN interlayers causes an increase in electrocatalytic activity. We investigated the bonding mechanism between carbon support and platinum using density functional theory and applied the d-band theory to understand the catalytic performance. Analysis of Pt's density of states and electronic population across layers sheds light on the catalytic behaviour of Pt nanoparticles, particularly in relation to their thickness and proximity to the g-CN support interface. Our simulation reveals an optimum thickness of ~11 Å, under which the catalytic performance deteriorates. [ABSTRACT FROM AUTHOR]

Featured Application: The findings presented in this work will allow the calculation of the electronic density states as well as the electrical and optical properties of complex one-dimensional coupled periodic potential wells without using expensive licensed software. The analytical generalization for N periodic potential wells coupled to a probe rectangular-like potential and a zero potential is extremely important in the study of one-dimensional periodic potentials in solid state physics, e.g., in the calculation of transport, optical, and magnetic properties. These findings raise the possibility of calculating equations for the generalization of N arbitrary potentials related to any potential V (x) using special functions as a solution. In this work, a novel analytical generalization of the transcendental energy equation, group velocity, and effective mass for N-coupled potentials to a probe one-dimensional potential V = V (x) was proposed. Initially, two well-known linear periodic potentials V = V (x) were employed to obtain analytical solutions for rectangular-like and Dirac-delta potentials. Python libraries were used to easily represent the equations for one or two rectangular-like potentials coupled with an arbitrary potential, highlighting the transcendental energy, group velocity, and effective mass. The results showed that the group velocity behavior changed its orientation due to the sign of the potential, whereas the width of the potential V (x) strongly influenced the group velocity behavior. The effective mass was also modified by the potential shapes, and their combinations, both effective mass and group velocity, exhibited similar physical behaviors to those found in ordinary rectangular-like potentials. [ABSTRACT FROM AUTHOR]

ZnO is one of the most promising mid-high temperature thermoelectric materials because of low cost, easy preparation and favorable chemical stability. Herein, the influence mechanism of Alkaline earth metal Ba doping on the thermoelectric properties of ZnO was studied. It is found that Ba doping can effectively improve the carrier mobility and electrical conductivity for that Ba doping can shorten the Zn–O bond and enhance the overlap and hybridization of electron orbitals. The electronic density of states of Zn and O is significantly enhanced. The highest power factor of ∼7.95 μWcm−1K−2 was obtained at 873 K, which is ∼1.4 times higher than that of the undoped sample. Due to the decrease of Young's modulus caused by Ba doping and the enhancement of phonon scattering of heavy element, the thermal conductivity decreases obviously in the whole temperature range. Ba doping enhanced the effect of phonon glass-electron crystal, and the ZT value of ∼0.345 was obtained at 873 K, which is ∼3.52 times as that of the pristine ZnO. The results indicated that alkaline earth metal doping is an effective way to improve the thermoelectric properties of ZnO functional materials. [ABSTRACT FROM AUTHOR]

To achieve n-type doping in diamond, extensive investigations employing first principles have been conducted on various models of phosphorus doping and boron–phosphorus co-doping. The primary focus of this study is to comprehensively analyze the formation energy, band structure, density of states, and ionization energy of these structures. It is observed that within a diamond structure solely composed of phosphorus atoms, the formation energy of an individual carbon atom is excessively high. However, the P-V complex substitutes 2 of the 216 carbon atoms, leading to the transformation of diamond from an insulator to a p-type semiconductor. Upon examining the P-B co-doped structure, it is revealed that the doped impurities exhibit a tendency to form more stable cluster configurations. As the separation between the individually doped atoms and the cluster impurity structure increases, the overall stability of the structure diminishes, consequently resulting in an elevation of the ionization energy. Examination of the electronic density of states indicates that the contribution of B atoms to the impurity level is negligible in the case of P-B doping. [ABSTRACT FROM AUTHOR]

In this work, we explore the electron scattering characteristics at interfaces between normal metals and topological semimetals in bulk as well as in thin film structures. We consider Cu/Ta and CoSi/Ta as representative metal/metal and topological semimetal/metal interface structures, respectively. For bulk interface structures, we find that metal/topological semimetal interfaces have roughly 20× higher interfacial resistivity than normal metal/metal interfaces primarily due to the low electronic density of states, the Fermi level in bulk topological semimetals. For thin films, we find that normal metal/metal interfacial resistivity shows a weak dependence on film thickness and is generally close to the corresponding bulk value. Interfaces between surface-conduction dominated topological semimetals, such as CoSi and normal metals in thin films, however, show decreasing interfacial resistivity with decreasing film thickness. This apparent reduction in interface resistivity originates from the surface-dominated transport, where the total transmission across the interface varies little with reduced film thickness, yielding an effective increase in interface conductivity at smaller dimensions. These results suggest that topological semimetals may be attractive candidates for next-generation interconnect materials with critically small dimensions where interfaces with other metals are ubiquitous. [ABSTRACT FROM AUTHOR]

Thermoelectric (TE) conversion technology, capable of transforming heat into electricity, is critical for sustainable energy solutions. Many promising TE materials contain rare or toxic elements, so the development of cost-effective and eco-friendly high-performance TE materials is highly urgent. Herein, we explore the thermal transport and TE properties of transition metal vanadate CuVO3 by using first-principles calculation. On the basis of the unified theory of heat conduction, we uncover the hierarchical thermal transport feature in CuVO3, where wave-like tunneling makes a significant contribution to the lattice thermal conductivity (κl) and results in the anomalously weak temperature dependence of κl. This is primarily attributable to the complex phononic band structure caused by the heterogeneity of Cu–O and V–O bonds. Simultaneously, we report a high power factor of 5.45 mW·K−2·m−1 realized in hole-doped CuVO3, which arises from a high electrical conductivity and a large Seebeck coefficient enabled by the multiple valleys and large electronic density of states near the valence band edge. Impressively, the low κl and the high power factor make p-typed CuVO3 have ZT of up to 1.39, with the excellent average ZT above 1.0 from 300 to 600 K, which is superior to most reported Cu-based TE materials. Our findings suggest that the CuVO3 compound is a promising candidate for energy conversion applications in innovative TE devices. [ABSTRACT FROM AUTHOR]

Thermoelectric (TE) conversion technology, capable of transforming heat into electricity, is critical for sustainable energy solutions. Many promising TE materials contain rare or toxic elements, so the development of cost-effective and eco-friendly high-performance TE materials is highly urgent. Herein, we explore the thermal transport and TE properties of transition metal vanadate CuVO3 by using first-principles calculation. On the basis of the unified theory of heat conduction, we uncover the hierarchical thermal transport feature in CuVO3, where wave-like tunneling makes a significant contribution to the lattice thermal conductivity (κl) and results in the anomalously weak temperature dependence of κl. This is primarily attributable to the complex phononic band structure caused by the heterogeneity of Cu–O and V–O bonds. Simultaneously, we report a high power factor of 5.45 mW·K−2·m−1 realized in hole-doped CuVO3, which arises from a high electrical conductivity and a large Seebeck coefficient enabled by the multiple valleys and large electronic density of states near the valence band edge. Impressively, the low κl and the high power factor make p-typed CuVO3 have ZT of up to 1.39, with the excellent average ZT above 1.0 from 300 to 600 K, which is superior to most reported Cu-based TE materials. Our findings suggest that the CuVO3 compound is a promising candidate for energy conversion applications in innovative TE devices. [ABSTRACT FROM AUTHOR]

The effective adsorption and treatment of toxic gases have attracted great attention amongst researchers, particularly the use of new two-dimensional materials for achieving the adsorption of toxic gases. We applied the density functional theory to investigate the stability, geometric structural, electrical, and magnetic properties of NH 3 molecules adsorbed on pristine, F-vacancy defected, and transition-metals (V, Cr, Mn, Y, Nb, and Mo) doped Zr 2 CF 2. The charge transfer and adsorption energy of the original substrate were low, indicating that the interaction between NH 3 and Zr 2 CF 2 was primarily physical adsorption. After introducing F-vacancy and TM-doping, the adsorption stability was enhanced, with the large charge transfer and high adsorption energies indicating that the adsorption of NH 3 transitioned to chemisorption. Electronic density of state diagrams suggested that the enhanced interaction was mainly caused by the hybridization of the d orbitals of dopants and p orbitals of the adsorbed NH 3 molecules. The adsorption energy of NH 3 molecules on Y-doped Zr 2 CF 2 was the highest at a value of −1.425eV, and the material was also explored as an adsorbent for NH 3 gas. After adsorbing six NH 3 molecules, the Y-doped substrate had an average adsorption energy of −1.350eV and still maintained a good thermal stability at a temperature of 300 K. These results can provide insights into the development of sensors and adsorbents based on MXenes. [Display omitted] • The adsorption of NH 3 on perfect Zr 2 CF 2 was physical adsorption. • The introduction of F-vacancy enhanced the adsorption stability of NH 3 molecule. • The doping of transition-metal (V, Cr, Mn, Y, Nb, Mo) significantly improved the sensitivity of Zr 2 CF 2 to NH 3 gas. • Y-doped Zr 2 CF 2 can be used as effective adsorbent to NH 3 gas. [ABSTRACT FROM AUTHOR]

The structural electrical and optical properties of AlXSb (x = Sc, P, Bi) are studied using density functional theory and the exchange—correlation approximation. We use the generalized gradient approximation (GGA-PBE) to compute optoelectronic characteristics of pure and (Sc, P, Bi)-doped materials. The structural features such as bulk moduli, pressure derivatives, and lattice parameters all agree well with the experiment's findings. Electronic state densities and band structure properties are determined using the GGA-PBE flavor. The calculations demonstrate that undoped AlSb is optically inactive because of the indirect (Γ-L) bandgap. When we doped appropriate materials such as Sc, P and B in pure AlSb, the bandgap shrinks and switches from an indirect bandgap to a direct bandgap (Γ-Γ), enabling the material to start functioning optically. The resultant material promised to be applicable for optoelectronic applications, such as photodetectors, light-emitting diodes, and high-power electronic devices. [ABSTRACT FROM AUTHOR]

Hydrogen-based compounds have been found to exhibit high superconducting critical temperature ( T c ) through the electron–phonon coupling mechanism under ultrahigh pressure. Herein, a new two-dimensional transition metal dichalcogenide material is constructed, namely, the Janus WSH monolayer. It is formed by replacing one layer of S atoms in the WS2 monolayer with H atoms. Then the electronic structure, phonon dispersion, electron–phonon coupling, and superconductivity are investigated by first-principles calculations. The results show that the introduction of H atoms helps to flatten the electronic dispersion and leads to high electronic density of states at the Fermi level, resulting in strong electron–phonon coupling. Additionally, the softening of phonon modes from the hybridization of in-plane W atomic vibrations and out-of-plane H atomic vibrations boosts the electron–phonon coupling further. The strong interactions between electrons and phonons lead to phonon-mediated superconductivity in Janus WSH monolayer with a calculated T c being about 23.1 K. This is the highest T c predicted in WS2-based materials at present, which indicates that hydrogenation is a great way to improve the T c of transition metal dichalcogenide materials. [ABSTRACT FROM AUTHOR]

Studies of the electronic structure and optical properties of the GdNiSb half-Heusler alloy have been performed. Calculations of the total and partial densities of electronic states were carried out on the basis of the GGA + U method, taking into account the correction for strong interactions in the f-electron system of gadolinium ions. By the method of spectral ellipsometry in the range of 0.078–5.64 eV, the dielectric functions of the alloy are investigated, their dispersion features are revealed. The anomalous behavior of optical conductivity in the infrared region of the spectrum for metals was found, confirming the presence of an energy gap at the Fermi level in the electronic spectrum, predicted in the calculation. A comparative analysis of the experimental and theoretical frequency dependences of optical conductivity is carried out, the features of interband light absorption are identified. The plasma frequency of conduction electrons is determined. [ABSTRACT FROM AUTHOR]

Doping rare earth elements in WC-Co cemented carbide can make the additives and the original elements form a complex structure, thus further strengthening the overall structure and improving the comprehensive properties of cemented carbide. In this paper, the rare earth element La is added to the cemented carbide WC-Co. Through the construction of atomic cell and interface, the influence of La element on WC-Co cemented carbides is analyzed. The influence law of La atom on other atoms is explained according to analyze the adhesion work, reaction enthalpy, electronic state density and charge density. The results show that more covalent bonds are generated near lanthanum atoms at the interface junction, which enhances the interface bonding strength, makes the whole structure more stable, and the unit cell doped with La element has better stability and improves the overall toughness. The calculation results can provide data for enhancing the performance of cemented carbides and provide a theoretical basis for doping rare earth lanthanum in WC-Co cemented carbides in the future. [ABSTRACT FROM AUTHOR]

Infrared (IR) detection is vital for various military and civilian applications. Recent research has highlighted the potential of two‐dimensional (2D) topological semimetals in IR detection due to their distinctive advantages, including van der Waals (vdW) stacking, gapless electronic structure, and Van Hove singularities in the electronic density of states. However, challenges such as large‐scale patterning, poor photoresponsivity, and high dark current of photodetectors based on 2D topological semimetals significantly impede their wider applications in low‐energy photon sensing. Here, we demonstrate the in situ fabrication of PtSe2/Ge Schottky junction by directly depositing 2D PtSe2 films with a vertical layer structure on a Ge substrate with an ultrathin AlOx layer. Due to high quality junction, the photodetector features a broadband response of up to 4.6 μm, along with a high specific detectivity of ~1012 Jones, and operates with remarkable stability in ambient conditions as well. Moreover, the highly integrated device arrays based on PtSe2/AlOx/Ge Schottky junction showcases excellent Mid‐IR (MIR) imaging capability at room temperature. These findings highlight the promising prospects of 2D topological semimetals for uncooled IR photodetection and imaging applications. [ABSTRACT FROM AUTHOR]

Grounded in research on B2 crystal structures, this study systematically substitutes the central 8 atoms with non-metallic Si atoms and metallic Fe atoms, exploring the resulting impacts on stress, magnetism, and energy across the entire crystal lattice. The positional permutations of these atoms are meticulously examined to elucidate their influence. Additionally, alterations in crystal parameters are analyzed through the lenses of energy band distribution and electronic density of states. Findings underscore that substituting non-metallic Si atoms with metallic Fe counterparts significantly increases stress, magnetism, and energy levels throughout the crystal lattice. Moreover, a positive correlation emerges between the quantity of replacements and the resulting stress levels, magnetic intensity, and energy. The arrangement of atoms demonstrates a substantial influence on material magnetism, with denser distributions yielding more pronounced effects on the overall system; individual arrangements are capable of increasing magnetism by approximately 23%. These insights are further validated by changes in energy band distribution and electronic state density, which show a continuous enhancement of metallic properties and reactivity as Si atoms are successively replaced by Fe atoms. This study introduces an innovative idea for enhancing material performance.

Using density functional theory calculation and rigid band model, we investigate the electronic structure and magnetostrictive properties of transition heavy-metal doped Fe-based (Fe–Al, Fe–Si, Fe–B, and Fe–Be) alloys. It is found that a small amount of addition of 4d/5d heavy-metal atoms greatly enhances the coefficient of tetragonal magnetostriction of Fe-based alloys, reaching up to about 1000 ppm in Fe87.5Al6.25Pt6.25 and Fe75Al18.75Rh6.25 alloys. The underlying mechanism is mainly ascribed to combined factors of band narrowing induced by non-bonded states in pure Fe layer, strong spin–orbit coupling effect by heavy metals, and improved mechanical properties, through analysis of the electronic density of states near Fermi level and k-mesh resolved magnetocrystalline anisotropy energy in momentum space. These results provide useful guidance for optimizing the magnetostrictive performance of Fe-based alloys for practical application. [ABSTRACT FROM AUTHOR]

We employ deep kernel learning electronic coarse-graining (DKL-ECG) with approximate Gaussian processes as a flexible and scalable framework for learning heteroscedastic electronic property distributions as a smooth function of coarse-grained (CG) configuration. The appropriateness of the Gaussian prior on predictive CG property distributions is justified as a function of CG model resolution by examining the statistics of target distributions. The certainties of predictive CG distributions are shown to be limited by CG model resolution with DKL-ECG predictive noise converging to the intrinsic physical noise induced by the CG mapping operator for multiple chemistries. Further analysis of the resolution dependence of learned CG property distributions allows for the identification of CG mapping operators that capture CG degrees of freedom with strong electron–phonon coupling. We further demonstrate the ability to construct the exact quantum chemical valence electronic density of states (EDOS), including behavior in the tails of the EDOS, from an entirely CG model by combining iterative Boltzmann inversion and DKL-ECG. DKL-ECG provides a means of learning CG distributions of all-atom properties that are traditionally "lost" in CG model development, introducing a promising methodological alternative to backmapping algorithms commonly employed to recover all-atom property distributions from CG simulations. [ABSTRACT FROM AUTHOR]

The experimental discovery of four-layer orthorhombic (4O) martensite has added new research motivation to the Ni–Mn–Sn magnetic shape memory alloy. Herein, the martensitic transformation, magnetic properties, and electronic structures of Ni2Mn1+xSn1−x alloys are investigated using the first-principles calculations. The results show that the increasing Mn content destabilizes the stability of austenite (A) compared to the non-modulated (NM) martensite. This composition adjustment promotes the occurrence of martensitic transformation in the range of 0.375 ≤ x ≤ 0.75, and the corresponding phase transition sequence is A → 4O → NM during cooling. An intense hybridization bond exists between excess Mn and its surrounding atoms. The increasing antiferromagnetic interaction between excess Mn and normal Mn weakens each atomic moment and, thus, the total magnetic moment. Furthermore, the physical essence of the phase stability and magnetic properties variation with composition was explained based on the electronic density of states. [ABSTRACT FROM AUTHOR]

As one of the earliest discovered two-dimensional materials possessing charge density wave (CDW), TiSe2 has attracted wide attention due to its superconductivity induced by Cu intercalation. Until now, the relationship between superconductivity and CDW remains unclear, largely due to insufficient research at extremely low temperatures and magnetic fields. In this study, spatially resolved electronic density of states (DOS) of Cu0.06TiSe2 is investigated using low-temperature scanning tunneling microscopy/spectroscopy measurements. It is found that short-ranged commensurate CDW coexists with a homogeneous superconductivity exhibiting an anisotropic s-wave gap with an amplitude of 0.5 meV. Compared to the parent compound TiSe2, the spectra of Cu0.06TiSe2 exhibit a clear electron doping effect, as evidenced by a 70 meV shift of Fermi energy. Interestingly, the DOS is found to be strongly modified near the Fermi energy, despite its overall rigid band nature. These findings suggest that it is the remnant electron–hole coupling that sustains the short-ranged CDW, while the doping enhanced DOS facilitates superconductivity. This reveals a momentum space competition between the two microscopically coexistent orders. [ABSTRACT FROM AUTHOR]

Herein, a first-principles pseudopotential plane-wave method is used to investigate the effects of co-doping Sc with Cu (or Zn) on the structural stability and desorption temperature of Mg-based hydrogen storage alloys and their hydride phases, as well as the related microscopic mechanisms. Specifically, the cell volume, electronic density of states, bond order, differential charge density, charge spreading, enthalpy of generation, and hydrogen desorption temperature of Mg 1.75 Sc 0.25 Ni 1−x M x H 4 (M = Cu or Zn, x = 0.125, 0.25, 0.375, and 0.5) are analyzed. Results indicate that the Mg 2 Ni alloy cell expands with an increase in the concentration of Cu or Zn co-doped with Sc. This expansion avoids the formation of a hydrogen adsorption layer, thus facilitating the entry and exit of hydrogen atoms from the alloy, thus improving its hydrogen release performance. In addition, the Cu or Zn atoms attract the surrounding H atoms and weaken the H–Ni bonds. Thus, the stability and dehydrogenation temperature of the system decrease with increasing Cu or Zn content. [Display omitted] • First-principles pseudopotential plane-wave method used to investigate Mg-based hydrogen storage materials. • The cell volume of the Mg 2 Ni alloy increases with increasing dopant content. • Co-doping Sc and M (M: Cu or Zn) in Mg 2 Ni weakens the bonding order of the H–Mg and H–Ni bonds. • Sc and M co-doping in Mg 2 Ni improves hydrogen release from the hydride phase. [ABSTRACT FROM AUTHOR]

A continuous quasi-equilibrium phase diagram δ(pO2, T) of a nonstoichiometric oxide La2NiO4 + δ with the layered perovskite-like Ruddlesden–Popper structure is obtained by the method of quasi-equilibrium oxygen release. The thermodynamic parameters are determined as a function of the oxide nonstoichiometry δ. Calculations are carried out within the framework of the localized-electron and itinerant-electron models which are used for description of the defect structure of ferrites and cobaltites, respectively. It is shown that the specific features of the phase diagram can be related to the electronic density of states near the Fermi level. [ABSTRACT FROM AUTHOR]

Nitrogen‐doped three‐dimensional graphene (N‐doped 3D‐graphene) is a graphene derivative with excellent adsorption capacity, large specific surface area, high porosity, and optoelectronic properties. Herein, N‐doped 3D‐graphene/Si heterojunctions were grown in situ directly on silicon (Si) substrates via plasma‐assisted chemical vapor deposition (PACVD), which is promising for surface‐enhanced Raman scattering (SERS) substrates candidates. Combined analyses of theoretical simulation, incorporating N atoms in 3D‐graphene are beneficial to increase the electronic state density of the system and enhance the charge transfer between the substrate and the target molecules. The enhancement of the optical and electric fields benefits from the stronger light‐matter interaction improved by the natural nano‐resonator structure of N‐doped 3D‐graphene. The as‐prepared SERS substrates based on N‐doped 3D‐graphene/Si heterojunctions achieve ultra‐low detection for various molecules: 10−8 M for methylene blue (MB) and 10−9 M for crystal violet (CRV) with rhodamine (R6G) of 10−10 M. In practical detected, 10−8 M thiram was precisely detected in apple peel extract. The results indicate that N‐doped 3D‐graphene/Si heterojunctions based‐SERS substrates have promising applications in low‐concentration molecular detection and food safety. [ABSTRACT FROM AUTHOR]

Stacking and twisting graphene layers allows to create and control a two-dimensional electron liquid with strong correlations. Experiments indicate that these systems exhibit strong tendencies towards both magnetism and triplet superconductivity. Motivated by this phenomenology, we study a 2D model of fluctuating triplet pairing and spin magnetism. Individually, their respective order parameters, d and N, cannot order at finite temperature. Nonetheless, the model exhibits a variety of vestigial phases, including charge-4e superconductivity and broken time-reversal symmetry. Our main focus is on a phase characterized by finite d ⋅ N, which has the same symmetries as the BCS state, a Meissner effect, and metastable supercurrents, yet rather different spectral properties: most notably, the suppression of the electronic density of states at the Fermi level can resemble that of either a fully gapped or nodal superconductor, depending on parameters. This provides a possible explanation for recent tunneling experiments in the superconducting phase of graphene moiré systems. P. Poduval et al. theoretically study the nonzero-temperature vestigial phases of a 2D model exhibiting both triplet superconductivity and magnetism. They show that this model allows for a unique superconducting state in which the condensate consists of entities with three electrons and one hole, with properties similar to those seen in experiments on moiré systems. [ABSTRACT FROM AUTHOR]

The electronic and transport properties of aluminum-graphene composite materials were investigated using the ab initio plane wave density functional theory. The interfacial structure is reported for several configurations. In some cases, the face-centered aluminum (111) surface relaxes in a nearly ideal registry with graphene, resulting in a remarkably continuous interface structure. The Kubo–Greenwood formula and space-projected conductivity were employed to study electronic conduction in aluminum single- and double-layer graphene-aluminum composite models. The electronic density of states at the Fermi level is enhanced by the graphene for certain aluminum–graphene interfaces, thus improving electronic conductivity. In double-layer graphene composites, conductivity varies non-monotonically with temperature, showing an increase between 300 and 400 K at short aluminum-graphene distances, unlike the consistent decrease in single-layer composites. [ABSTRACT FROM AUTHOR]

The surface topography and density of unoccupied electronic states at thermal deposition of ultrathin dibromo-bianthracene films on the ZnO surface have been studied. The electronic characteristics of unoccupied electronic states during growth of dibromo-bianthracene films to a thickness of 10 nm have been investigated by total current spectroscopy using a probe electron beam. The experimental dependences have been analyzed using theoretical calculation of the orbital energies for dibromo-bianthracene molecules by the method of density functional theory (DFT). [ABSTRACT FROM AUTHOR]