In this work, we use density functional theory (DFT) to thoroughly analyze the structural, electrical, optical, and thermoelectric characteristics of halide double perovskites Rb2AsAuX4 (X = Br, Cl). Both compounds' structural stability is confirmed by the optimized lattice characteristics, with Rb2AsAuBr4 showing somewhat larger cell dimensions than Rb2AsAuCl4. Indirect band gaps of 0.338 eV (Br) and 0.885 eV (Cl), which are within the optimal range for solar applications, are shown by electronic band structure simulations. Strong absorption coefficients in the visible region above 1.2 × 101 cm-1 are shown in optical spectra, suggesting great potential for solar energy harvesting. High Seebeck coefficients of up to 310μV/K (Br) and 285μV/K (Cl) at ambient temperature are shown by thermoelectric analysis, together with electrical conductivities that facilitate effective charge transfer. Thermoelectric performance is further improved by the comparatively low thermal conductivity (0.9-1.1 W/m·K). Together, our findings demonstrate Rb2AsAuX4's versatility and establish Rb2AsAuBr6 and Rb2AsAuCl4 as viable options for next optoelectronic and energy-harvesting applications.

High-pressure transition from metallic to semiconductor in newly discovered stable NaRuH3: Electronic band structure, elastic constants and mechanical properties

Theoretically, introducing inhomogeneous magnetization into magnetic topological Weyl semimetals can dramatically enhance the anomalous Hall conductivity owing to the chiral-gauge field effect. However, an enhancement strategy remains elusive. Here, we demonstrate the successful generation of inhomogeneous magnetization in a recently discovered magnetic Weyl semimetal Co3Sn2S2 by introducing a dopant with strong spin-orbit coupling. The giant anomalous Hall angle reached 42% at 130 K, even under a relatively weak magnetic field (∼0.1 T), making it the highest reported value. Theoretical and magnetic microstructure analyses suggest that the significantly enhanced anomalous Hall effect may be due to the chiral-gauge field induced directly by inhomogeneous magnetization in real-space. Furthermore, considering the electronic band structure of Co3Sn2S2 and the chiral-gauge field, the theoretical Hall resistivity is quantitatively in good agreement with the experimental value. This study demonstrated the feasibility of dramatically manipulating the physical properties of Anomalous-Hall-angmagnetic topological materials using magnetic microstructure engineering.

Holey MXenes have recently emerged as a promising extension of the MXene family, in which in‐plane porosity enhances ion transport, exposes defect‐rich edges, and can create confined domains useful for modulating reactivity. In this work, we present a systematic density functional theory and ab initio molecular dynamics (AIMD) investigation of the structural and electronic properties of holey Ti 3 C 2 O 2 and Ti 2 CO 2 MXenes. Edge stability was assessed through nanoribbon models, revealing that OTiC–TiCO edges reconstruct into Ti 3 O tetrahedra and represent the most stable configuration. Hole formation energies were evaluated for pores of increasing size up to approximately 2.1 nm, showing enhanced stability with increasing pore size, and oxygen‐rich walls stabilise the pores. TiO bond lengths and charges are nearly identical at edges and pore walls, highlighting their chemical similarity. Electronic band structures indicate that metallic behaviour is preserved for all edge and hole models, independent of porosity, consistent with experimental observations for titanium carbide MXenes. AIMD simulations at 300 K further demonstrate the thermal stability of holey MXenes and highlight the tendency of undercoordinated sites to attract terminations. Our results provide atomistic insights into the stability and electronic resilience of holey MXenes, advancing their rational design for applications in catalysis, sensing, and energy storage.

Covalent organic frameworks (COFs) hold exceptional potential for humidity sensing due to their tunable chemical structure and high porosity, yet their uncontrolled relationships between molecular design, nanoscale architecture, and sensing performance have hindered their practical applications. Here, we report the rational molecular engineering of wafer-scale, ultrathin 2D imine-linked COF films via interfacial polymerization, illustrating precise control over electronic band structure, nanoscale porosity, and hygroscopicity for exceptional humidity sensing, thus unveiling the underlying structural-property correlations. By simultaneously incorporating triazine and multi-hydroxyl groups, the humidity sensor based on 2D COFTPT-THTA exhibits a high sensitivity (66124% per %RH), fast response/recovery times (0.12/0.40 s), and minimal hysteresis (ΔRH ≈ 1.0%), due to a synergistic effect of high structural polarity, excellent hydrophilicity, and the nanoscale confined crystalline pore framework. The nanometer-scale thickness and ultrasmooth surface facilitate efficient charge transport and water adsorption kinetics. Leveraging these properties, we further demonstrate a prototypical wearable sensor for real-time respiratory monitoring, which is capable of accurately tracking physiological states and detecting pathological patterns (asthma, apnea). This work establishes a fundamental molecular engineering paradigm for 2D COF film-based sensors, bridging the gap between programmable materials and next-generation high-performance health diagnostics.

We explored the structural, electronic, mechanical and thermoelectric properties of NbRuX (X [Formula: see text] P, As, Sb, Bi) half-Heusler (HH) alloys utilizing density functional theory (DFT)-based quantum ESPRESSO (QE). We used the Perdew–Burke–Ernzerhof (PBE) functional within the generalized gradient approximation (GGA). Ground state energy calculations show the stability of the compounds, while elastic constant calculations confirm mechanical stability and their ductile nature across the series. The calculated lattice parameters for NbRuX (X [Formula: see text] P, As, Sb, Bi) are found to be 5.84, 5.97, 6.19 and 6.32 Å, respectively. Narrow indirect band gaps between 0.25 and 0.43[Formula: see text]eV are observed in the electronic band structure and density of states, indicating suitability for thermoelectric performance. Vibrational properties calculated using the thermo_pw code show the dynamic stability. Also, using the BoltzTraP code, we determined thermoelectric parameters. Thermoelectric analysis highlights high Seebeck coefficients and power factors, with NbRuBi showing the largest Seebeck coefficient of 640[Formula: see text][Formula: see text]V/K at 300[Formula: see text]K and NbRuP exhibiting the maximum power factor of [Formula: see text][Formula: see text]W/mK 2 at 300[Formula: see text]K. Here, NbRuSb achieves the highest electronic figure of merit (ZT [Formula: see text] 0.95) among all the HH alloys. Results suggest that NbRuX alloys are promising candidates for next-generation thermoelectric applications.

The physics of phase transitions in low-dimensional systems has long been a subject of significant research interest. Long-range magnetic order in the strict two-dimensional limit, whose discovery circumvented the Mermin-Wagner theorem, has rapidly emerged as a research focus. However, the demonstration of a non-trivial topological spin textures in two-dimensional limit has remained elusive. Here, we demonstrate the out-of-plane electric field breaks inversion symmetry while simultaneously modulating the electronic band structure, enabling electrically tunable spin-orbit interaction for creation and manipulation of topological spin textures in monolayer CrI3. The realization of ideal two-dimensional topological spin textures may offer not only an experimental testbed for probing the Berezinskii-Kosterlitz-Thouless mechanism, but also potential insights into unresolved quantum phenomena including superconductivity and superfluidity. Moreover, voltage-controlled spin-orbit interaction offers a novel pathway to engineer two-dimensional spin textures with tailored symmetries and topologies, while opening avenues for skyrmion-based next-generation information technologies.

Graphene's remarkable two-dimensional nature, protected by time-reversal and space-inversion symmetries, has revolutionized our understanding of electronic band structures. Graphene, as the prototypical semimetal, has inspired a surge of interest in searching for exotic electronic states in three-dimensional materials through simple yet powerful low-energy effective Hamiltonians. In this pedagogical work, we extend these ideas to explore the electronic band structures with the exact solution of density of states, and effective masses of three fascinating classes of topological semimetals-Dirac semimetals (DSM), Weyl semimetals (WSM), and nodal line semimetals (NLS). By adopting model Hamiltonians, we present a clear and accessible framework that invites beginners to engage with the rich physics of these systems, while also connecting theoretical insights to experimental realizations. We have also provided interesting exercises (in the SI) with proper hints to extend the technique further and go beyond what will be learnt here. We hope that this study will not only deepen appreciation for the emergence of novel band structures in modern condensed matter research, but also encourage educators to bring research-inspired perspectives into the classroom. Such integration can enrich undergraduate education by exposing students early to cutting-edge concepts and methodologies, nurturing curiosity and innovation at the interface of learning and discovery.

The sluggish O2 reduction reaction (ORR) that occurs in fuel cells requires an efficient electrocatalyst to increase the efficiency of the fuel cells. It is necessary to replace the widely acknowledged Pt-based electrocatalyst with a low-cost, non-precious metal-based electrocatalyst to efficiently catalyze the ORR. Herein, we propose a material comprising Fe–Ce nanoparticles encapsulated within a carbon nanotube, e.g., FeCe@CNT, as a promising electrocatalyst for the ORR. The structural and electronic properties, i.e., electronic band structure and total density of states (DOS), of the FeCe@CNT material were studied by employing a first-principles-based DFT-D3 method. Our current study found that the FeCe@CNT material has conducting properties due to its zero electronic band gap (Eg). The electronic bands cross the Fermi energy level (EF) with a large electron density of states around the Fermi level in total DOS, confirming the conducting nature of the subject material. This study explored all the reaction steps involved in the ORR mechanism on the surface of the FeCe@CNT system. The O2 adsorption on the surface of the FeCe@CNT system occurred with an adsorption energy (ΔE) of −1.67 eV. This study found that the ORR mechanism on the surface of the FeCe@CNT material proceeds through the four-electron (4e−) transfer mechanism. The associative pathway of the ORR, along with various reaction intermediates, was explored using the adsorption energy. Our energy calculation demonstrates that the active sites on the FeCe@CNT material are thermodynamically favorable for catalyzing the ORR. Our study found that the FeCe@CNT material is a potential candidate that can be used in the fuel cell as a cathodic electrode material. The valuable insights from the strong FeCe nanoparticle interaction with the CNT will help advance the interfacial design of novel electrocatalysts towards the ORR.

First-principles calculations were performed to investigate the structural, electronic, mechanical, and spintronic properties of InTeX (X = Cl, Br, and I) monolayers formed via full halogenation of pristine InTe. Halogenation induces a structural transformation from the four-sublayer Te-In-In-Te configuration to a three-sublayer Te-In-X geometry, accompanied by the formation of polar covalent In-X bonds and the suppression of metallic In-In interactions. The resulting monolayers preserve a buckled hexagonal lattice and exhibit enhanced thermodynamic, thermal, and dynamical stability. InTeX monolayers display moderate Young's moduli (22.18-25.26 N m-1), isotropic in-plane elastic behavior, and Poisson's ratios from 0.31 to 0.32, rendering them promising candidates for flexible and wearable nanoelectronic applications. The electronic band structures reveal tunable direct band gaps and strong, anisotropic Rashba spin-orbit coupling, with Rashba parameters α R ranging from 0.81 to 1.04 eV Å, indicating potential for spintronic and optospintronic devices. Importantly, charge-carrier mobilities were evaluated by explicitly accounting for phonon and impurity scattering, yielding realistic values consistent with experimental expectations and underscoring the importance of accurate mobility modeling for device performance. Overall, the combination of structural stability, tunable electronic properties, robust spin-orbit effects, and reliable carrier transport makes InTeX monolayers highly promising materials for future research in flexible electronics, spintronics, and multifunctional two-dimensional nanomaterials.

We present a comprehensive density functional theory investigation of cubic perovskites A3PX3(A = Ca, Sr; X = Cl, F) to explore the influence of cation-anion substitution on their structural, mechanical, electronic, and optical properties. Structural optimization confirms lattice expansion when substituting Ca with Sr and F with Cl. Electronic band structure calculations reveal direct band gaps at the Γ point, with values 1.85 eV (2.90 eV) for Ca3PF3, 2.06 eV (2.97 eV) for Sr3PF3, 1.96 eV (2.77 eV) for Sr3PCl3, using the PBE (HSE06) functional, respectively. These results demonstrate that substituting both the A-site cation and the X-site anion provides a straightforward route for tuning the band gap within the visible range. Optical analyses show that substitution also modulates dielectric response, absorption onset, and optical conductivity, while mechanical calculations confirm elastic stability with higher stiffness for Ca-F rich compounds compared to Sr-Cl systems. Overall, this dual substitutional strategy underscores the promise of A3PX3perovskites as stable and tunable candidates for photovoltaic and optoelectronic applications.

An A- and B-site-ordered quadruple perovskite oxide LaCu3Ni2Re2O12 was synthesized at 9 GPa and 1323 K. The crystal structure adopts a cubic space group of Pn-3 with the lattice constant a = 7.4961(1) Å. Bond valence sum calculation and X-ray absorption spectroscopy suggest the charge distribution to be La3+Cu2+3Ni2+2Re5.5+2O12. A ferrimagnetic transition arising from the Cu2+(↑)-Ni2+(↑)-Re5.5+(↓) spin coupling is found to occur at a Curie temperature of TC ≈ 210 K. First-principles calculations suggest a half-metallic electronic band structure for LaCu3Ni2Re2O12 with an energy gap of about 1.9 eV at the up-spin channel and a conducting band at the down-spin channel. By comparison with other isostructural LaCu3B2Re2O12 (B = Fe, Co, Ni) perovskites, we find that the electronic configuration of Re dominates the Curie temperature, as well as the half-metallic band gap.

Multi-band valley engineering offers an effective route to achieving high thermoelectric performance; however, the associated increase in the density-of-states effective mass (m*) inevitably compromises carrier mobility (µ), posing a fundamental challenge for further enhancement of the figure of merit (ZT). Here, Ga doping is employed to tailor the electronic band structure in Ge0.94Bi0.06Te, inducing the simultaneous convergence of three valence band edges and the emergence of a midgap band, which markedly enhances m* and the Seebeck coefficient. Reduced electron localization arising from Ga-Te bonding, together with interfaces featuring small lattice mismatch, effectively mitigates carrier scattering and preserves a high µ. As a result, an optimized balance between m* and µ yields an outstanding weighted mobility and power factor. Furthermore, Ga-induced lattice vibration disorder, in synergy with engineered multi-scale crystal defects, strongly suppresses the lattice thermal conductivity. Consequently, a high ZT exceeding 2.1 is achieved at 653 K. A single-stage lead-free device based on the optimized material delivers a competitive power conversion efficiency of 7.7% under a temperature difference of 440 K. This study provides new insights into the rational design of high-performance lead-free thermoelectric materials and devices.

Machine learning approach for vibronically renormalized electronic band structures

Hydrogen is a possible clean energy solution to mitigate the global energy problem and environmental issues. The Mg 2 QH 6 (Q= Cr, Mn) hydrides have attracted interest due to their substantial hydrogen storage capabilities and advantageous characteristics. The pressure-induced physical characteristics of Mg 2 QH 6 (Q= Cr, Mn) have been methodically examined by density functional theory (DFT) to assess their viability for hydrogen storage and energy-related applications. A comprehensive examination of their structural stability, hydrogen storage properties, electronic band structures, optical absorption characteristics, elastic constants, mechanical stability, and thermodynamic aspects was conducted at applied pressures from 0 to 40 GPa. The gravimetric hydrogen storage capacities of Mg 2 CrH 6 and Mg 2 MnH 6 are determined to be 5.67 and 5.52 wt%, demonstrating their significant prospects for practical hydrogen storage applications. The electronic structure simulations validate the metallic characteristics of both Mg 2 CrH 6 and Mg 2 MnH 6 hydrates over the whole pressure spectrum, signifying exceptional electrical conductivity, beneficial for electrochemical and catalytic applications. The imaginary component of the dielectric function displays pronounced peaks at 8.682 eV (40 GPa) for Mg 2 CrH 6 and 8.335 eV (40 GPa) for Mg 2 MnH 6 , indicating robust optical activity. Thermodynamic analysis confirms the stability of both substances under pressure. The elastic and mechanical evaluations validate their stability and ductility under compression, affirming their dependability under highpressure conditions. These theoretical findings offer significant insights into the pressure-tunable properties of Mg 2 QH 6 hydrides, underscoring their potential for complex hydrogen storage systems and multifunctional optoelectronic devices.

We have reported fundamental aspects on the vacancy-mediated conduction and relaxation mechanisms of charge carriers in 2D RbPb2Br5 layered-halides synthesized via the wet chemical method. The structural deformation and phase transition are not observed in RbPb2Br5 layered-halides from temperature dependence of the x-ray diffraction and differential scanning calorimetry results, respectively. The electronic band structure and total density of states are theoretically calculated and the obtained bandgap from the calculation is around ∼2.89 eV. The impedance results provide the grain and grain boundary contributions to the effective impedance in details. The temperature dependence of the DC conductivity (σDC) and the hopping frequency (ωH) in the different temperature regions is explained by the predominance of the vacancy-mediated charge carrier conduction and relaxation due to the trap states formed by various defects in the layered-halide. The calculated activation energy for the DC conductivity in the low-temperature region (Eσ,LTR ∼ 0.075 eV) is comparatively lower than those obtained in the mid-temperature (Eσ, MTR ∼ 0.58 eV) and high-temperature regions (Eσ, HTR ∼ 1.06 eV). The high value of the activation energy at high temperatures is observed due to the onset of vacancy-mediated charge carrier conduction, leading to high DC conductivity. Furthermore, the value of the activation energy obtained from DC conductivity is much closer to those obtained for the hopping frequency and the dielectric relaxation time in different temperature regions.

Abstract The anomalous Hall and Nernst effects provide critical probes for investigating the Berry-curvature-related electronic band characteristics in magnetic materials. In this study, we conducted a comprehensive investigation into the magnetic, electrical, and thermal transport properties of $\mathrm{NdCrGe}_3$ single crystals with Ge-based breathing kagome lattice. This compound undergoes a ferromagnetic transition at 128 K, and the magnetic ordering of the Nd sublattice emerges below 100 K . Transport measurements indicate that $\mathrm{NdCrGe}_3$ manifests large anomalous Hall conductivity with $\sigma_{x y}^{\mathrm{A}} \approx 380 \Omega^{-} { }^1 \mathrm{~cm}^{-1}$ at low temperatures and anomalous Nernst coefficient with $\left|S_{x y}^{\mathrm{A}-\mathrm{max}}\right|=0.74 \mu \mathrm{V} / \mathrm{K}$ at 100 K . Scaling analysis reveals that $\mathrm{NdCrGe}_3$ exhibits large intrinsic anomalous Hall conductivity of $\sim 260 \Omega^{-1} \mathrm{~cm}^{-1}$ and falls within the intrinsic regime of the unified model. Furthermore, the anomalous Nernst coefficient breaks down the scaling relationship with magnetization observed in conventional ferromagnets, while the anomalous Nernst conductivity manifests a scaling behavior of $T \ln T$. These results demonstrate that the anomalous transverse transport properties of $\mathrm{NdCrGe}_3$ are predominantly governed by the intrinsic Berry mechanism. Our systematic investigations elucidate that $\mathrm{NdCrGe}_3$ exhibits relatively strong Berry curvature, which is related to its electronic band structure.

This study investigates the structural, electronic, mechanical and thermoelectric properties of a two-dimensional h-TaN monolayer using first-principles density functional theory and Boltzmann transport theory. The electronic band structure shows a direct band gap of 0.61 eV without spin-orbit coupling (SOC), which becomes an indirect band gap of 0.39 eV with SOC. The mechanical analysis confirms that the h-TaN monolayer is elastically stable and isotropic, exhibiting a moderate Young’s modulus of 103.78 N/m and a Poisson’s ratio of 0.30, indicating a favorable balance between stiffness and exibility. Thermoelectric performance evaluated for n- and p-type doping at a fixed carrier concentration of 1 × 10 20 cm –3 over the temperature range of 250-700 K with or with-out SOC. With SOC, the p-type h-TaN monolayer demonstrates superior thermoelectric performance, achieving a maximum conversion efficiency of 8.81% at 700 K, compared to 5.93% for the n-type. The lattice thermal conductivity decreases significantly from 3.27 W/m·K at 300 K to 1.31 W/m·K at 700 K. These results highlight the dominant role of p-type carriers and establish h-TaN as a mechanically robust and promising candidate for nanoscale thermoelectric devices.

ABSTRACT The design of efficient electrode nanomaterials for energy devices necessitates precise control over their electronic properties. Achieving this requires accurate manipulation of the Fermi level ( E F ) through modulation of the electronic band structure, a strategy referred as E F ‐engineering. Herein, designing of hollow nanorods (Mo‐Sn‐Zn‐S Hollow Nanorods, designated as MSZS) of Zn and S dual vacancies (V Zn+S ) incorporated MoS 2 composite is introduced, where the larger cationic sizes of Zn and Sn than that of Mo induce V Zn+S and subsequently lattice expansion to achieve precise E F ‐engineering. These defects significantly enhance the material's electrical and ionic conductivity. Besides, the novel hollow structure of MSZS offers large sodium‐ion migration channels with a low sodium‐ion diffusion kinetic barrier, making the MSZS as a promising anode material for sodium‐ion batteries (SIBs). Therefore, the novel V Zn+S incorporated MSZS anode delivers a high capacity of 854 mAh g −1 at 0.5 C (99.14% retention after 100 cycles), and a superior high‐rate stability of 614 mAh g −1 at 4 C (82.3% retention after 500 cycles). The synergy of defects, hollow morphology, and E F engineering contributes to its performance, inspiring the design of precisely engineered electrodes for advanced energy storage.

ABSTRACT Skutterudites are promising thermoelectric candidates for medium‐temperature energy conversion owing to their excellent mechanical strength and thermal stability, yet their practical deployment is hindered by their moderate thermoelectric performance. Herein, we report a synergistic optimization of the electronic band structure and phonon scattering in Yb‐filled skutterudites through simultaneous indium filling and Te doping. This dual strategy delivers an exceptional figure of merit ( zT ) of ∼1.72 at 773 K, arising from a high power factor of 5.63 mW m −1 K −2 and a markedly suppressed total thermal conductivity of 2.23 W m −1 K −1 . First‐principles calculations reveal that In filling and Te doping cooperatively converge electronic bands, thereby enhancing electrical transport, while advanced electron microscopy uncovers the formation YbTe nanoprecipitates and associated lattice distortions that intensify phonon scattering. A 7‐pair single‐stage thermoelectric device fabricated from the optimized materials achieves an ultra‐high energy conversion efficiency of 8.2% under a temperature difference of 380 K. These findings establish a clear structure‐property‐performance correlation and provide a versatile strategy for propelling skutterudites toward high‐efficiency, device‐level applications.