We systematically investigate the microscopic origins of the intrinsic anomalous Hall effect (AHE) and spin Hall effect (SHE) in the rare-earth transition-metal (RE–TM) ferrimagnet ${\mathrm{GdCo}}_5$ using first-principles $\mathrm{DFT}+\mathrm{U}+\mathrm{J}$ calculations combined with Berry-curvature analysis. The Hall-active states near the Fermi energy in the ground-state antiparallel ferrimagnetic configuration are predominantly Co-derived. However, changes in the relative Gd–Co magnetic alignment substantially reconstruct these electronic states, modifying the relevant band dispersions and interband energy separations and thereby redistributing the Berry curvature and Hall response. Based on this mechanism, we elucidate the microscopic origin of the pronounced suppression of the anomalous Hall conductivity (AHC) during the field-induced spin-flop transition, showing that the dominant reduction occurs in the first stage of spin reorientation, despite the Gd–Co antiparallel alignment remaining largely preserved. At the Fermi energy, the AHC reaches its maximum magnitude of $885{\left(\mathrm{\Omega }\mathrm{cm}\right)}^{-1}$ in the antiparallel ground state. Furthermore, we show that ${\mathrm{GdCo}}_5$ exhibits a large intrinsic spin Hall conductivity (SHC), with the dominant tensor components reaching ${\sigma }_{zx}^y=1558\left(\hslash /\mathrm{e}\right){\left(\mathrm{\Omega }\mathrm{cm}\right)}^{-1}$ and ${\sigma }_{yx}^z=731\left(\hslash /\mathrm{e}\right){\left(\mathrm{\Omega }\mathrm{cm}\right)}^{-1}$ at the Fermi level, yielding a substantial spin Hall angle up to 0.13. In addition, selected SHC tensor components can be strongly modulated and even reversed in sign through magnetization rotation and changes in the relative Gd–Co alignment, reflecting the sensitivity of the spin Hall response to the magnetic Laue group symmetry and relative sublattice configuration. Our findings reveal a microscopic connection between magnetic configuration, electronic-structure reconstruction, and Berry-curvature-driven transport in ${\mathrm{GdCo}}_5,$ and highlight its potential for exploring magnetization-dependent intrinsic spin-current generation.

Laser ignition of energetic crystals involves coupled photophysical and chemical processes, beginning with photothermal conversion that transfers photoexcited-carrier energy to lattice vibrations and initiates local heating before decomposition. Here, first-principles calculations elucidate how intrinsic defects regulate this process in the quasi-two-dimensional molecular energetic crystal 1,3,5-triamino-2,4,6-trinitrobenzene (TATB). Atomic vacancies introduce in-gap states, with hydrogen vacancies efficiently trapping both electrons and holes and thereby promoting defect-assisted nonradiative recombination. Mode-resolved analysis shows that recombination at these defects preferentially couples to intramolecular vibrations associated with molecular deformation. By contrast, slower recombination in pristine TATB couples mainly to low-frequency interlayer collective modes, whose energy must be redistributed into higher-frequency intramolecular vibrations through phonon–phonon interactions. Thus, defects accelerate carrier-to-lattice energy transfer and directly channel the released energies into vibrations relevant to chemical-bond cleavage during the initial photothermal stage of laser ignition.

Charge carriers in organic semiconductors form polarons, which are self-localized states stabilized by interactions with their environment. Using a dielectric-stabilized tight-binding model parametrized from first-principles calculations, we compute ground and excited polaron states in poly(3-hexylthiophene) (P3HT). Our results quantitatively reproduce key midinfrared absorption features, notably the chain-length-dependent shift of the intrachain polaron excitation peak (peak B) and its variation between regioregular and regiorandom P3HT. Comparison to an alternative stabilization mechanism based on local ring distortions reveals that dielectric polarization dominates polaron formation, as ring distortions yield insufficient binding and excitation energies inconsistent with experiments. These findings clarify the microscopic origin of polarons in conjugated polymers and provide a predictive framework linking polaron energetics to spectroscopic observables, advancing the understanding of charge transport in organic semiconductors.

Cement paste serves as the universal binder in concrete, formed by mixing water with Ordinary Portland Cement (OPC). In its fresh state, cement paste behaves as a reactive suspension in which cement grains continuously dissolve, while colloidal calcium silica-hydrate (C-S-H) particles precipitate and progressively build a percolated load-bearing structure that densifies and hardens through hydration. Like many colloidal gels and concentrated suspensions, cement paste is sensitive to external stimuli such as mechanical vibrations and temperature variations. Here, we investigate the impact of power ultrasound (PUS) applied to OPC paste during the very early stages of hydration on the micromechanical properties of the hardened material. Fresh cement pastes are exposed to PUS at different amplitudes and durations before curing for 28 days. Microindentation testing reveals a progressive degradation of hardness, indentation modulus, and creep modulus with increasing PUS exposure. Remarkably, all mechanical properties collapse onto master curves controlled by the cumulative ultrasonic exposure. Microscratch testing further reveals enhanced acoustic-emission activity in sonicated samples, consistent with the development of additional mesoscale defects within the hardened material. In contrast, nanoindentation measurements show that the intrinsic mechanical properties of the individual phases composing the hardened paste—low-density and high-density C-S-H—remain largely unaffected. Together, these results indicate that PUS primarily alters the microstructure of hardened cement paste at scales larger than those of the hydration products themselves. These findings offer valuable experimental insights into novel pathways for modifying the mechanical properties of reactive colloidal gels.

Narrow-bandgap thermoelectric semiconductors typically suffer from excessively high intrinsic carrier density, which severely suppresses the Seebeck coefficient and compromises the power factor. Decoupling the entangled electronic parameters to resolve this intrinsic trade-off remains a central challenge in the pursuit of high-performance materials. Here, using $n$-type Te-free BiSe as a model system, we demonstrate a “staged dual-doping” strategy to decouple the regulation of carrier density and density of states (DOS) effective mass. We show that initial Sb alloying successfully mitigates the excessive carrier density, boosting the Seebeck coefficient and carrier mobility, yet inevitably reducing the DOS effective mass. Crucially, subsequent Ge incorporation recovers this compromised effective mass by modulating the band structure while simultaneously inducing hierarchical microstructural heterogeneities ranging from point defects to dislocations that strongly scatter phonons. As a result, the optimized ${\mathrm{Bi}}_{0.69}{\mathrm{Sb}}_{0.29}{\mathrm{Ge}}_{0.01}\mathrm{Se}$ achieves a peak $\mathit{ZT}$ of 0.54 at 473 K, a room-temperature $\mathit{ZT}$ of 0.33, and an average $\mathit{ZT}$ of 0.48 over 300–523 K. This work establishes a rational, scalable pathway for optimizing Te-free BiSe and offers a transferable blueprint for managing trade-offs in narrow-bandgap thermoelectrics.

Non-fullerene acceptors such as Y6 have enabled high-efficiency organic photovoltaic devices and motivated the development of single-component architectures; however, the microscopic mechanisms governing exciton transport and charge dissociation remain under active investigation. In particular, the interplay between Frenkel and charge-transfer excitations and their coupling to environmental fluctuations complicates the description of light absorption and subsequent exciton dynamics. Here, ultrafast transient absorption spectroscopy is used to probe exciton quenching dynamics in Y6 films interfaced with hole-transport layers. To interpret these measurements, we develop an analytical model based on hybrid Frenkel-charge-transfer states that enables direct extraction of intermolecular electronic couplings, charge-transfer character, and system-bath interaction strengths from experimental data. The analysis reveals a substantial charge-transfer admixture of 20–40 % in the exciton states and identifies delocalization-mediated transport on the short length and time scales probed by the measurements. Consistent with this interpretation, the corresponding quenching dynamics occur on a $\sim 1$ ps timescale within $\sim 4\mathrm{nm}$ of the interface, suggesting a short-range injection mechanism facilitated by exciton delocalization. In addition to providing physical parameters for Y6, these results establish a quantitative framework that connects spectroscopic observables to microscopic transport mechanisms and can be generalized to other non-fullerene acceptors.

Polar materials have recently attracted significant interest due to their rich multifunctional properties. The chalcogenide polar semiconductor ${\mathrm{Cu}}_{1-x}{\mathrm{Mn}}_{1+y}{\mathrm{SiTe}}_3$ (Cu-deficient, $0.04\le x\le 0.26$; $0.03\le y\le 0.15$) is an emerging multiferroic system in which electric polarization is coupled to magnetization. However, its macroscopic ferroelectric polarization is strongly suppressed due to the presence of a high density of stacking faults. In this work, we demonstrate that these crystal defects, likely originating from nonstoichiometry, can be substantially reduced by increasing the Cu content. Cu-enriched samples, ${\mathrm{Cu}}_{1+x}{\mathrm{Mn}}_{1-y}{\mathrm{SiTe}}_3$ ($0.04\le x\le 0.3;0.13\le y\le 0.31$), crystallize in a noncentrosymmetric monoclinic structure (space group $\mathit{Pm}$) as the Cu-deficient counterpart but show a nearly stacking-fault-free phase, which is attributed to the emergence of an interstitial site. Consequently, the Cu-enriched samples show a pronounced enhancement of the second-harmonic generation (SHG) response compared to Cu-deficient compositions. Magnetically, the Cu-enriched crystals retain long-range antiferromagnetic order with a Néel temperature of $T_{\mathrm{N}}\sim 33$ K without a glassy state but manifest a distinct metamagnetic transition along the polar $b$ axis that is absent in the Cu-deficient compositions. Furthermore, the electronic ground state evolves from insulating to doped semiconducting behavior upon Cu enrichment. Together, these results establish this material system as a unique and versatile platform for elucidating the interplay among composition, crystal defects, and multifunctional properties, offering a route to design magnetic polar systems with tunable quantum functionalities.

Heterointerfaces are ubiquitous in modern devices, found in technologies ranging from microelectronics to structural components for energy applications. Many of these emerging technologies are found in applications that are subject to harsh environments, such as satellites, batteries, and next-generation nuclear reactors. In some scenarios, multiple extreme conditions, such as irradiation and corrosion, act on the material simultaneously. Extending the lifetime of these technologies is dependent on a detailed understanding of how their component materials platforms and interfaces respond in extreme environments, where irradiation and corrosion may couple in unique ways, distinct from corrosion under ambient conditions. Oxides, which form readily over metal underlayers, can act as protective coatings; enhancing the robustness of oxide overlayers to protect underlying metal alloys is a potential avenue towards corrosion mitigation. Here, we study the impact of irradiation-induced nonequilibrium defects on charge segregation and electric fields at and near multi-phase oxide heterointerfaces. We perform a detailed study of irradiated ${\mathrm{Fe}}_2{\mathrm{O}}_3–{\mathrm{Cr}}_2{\mathrm{O}}_3$ thin film heterostructures using first-principles density functional theory (DFT) electronic structure modeling paired with four-dimensional-scanning transmission electron microscopy (4D-STEM) differential phase contrast (DPC) and electron energy loss spectroscopy (EELS) techniques to measure nanoscale changes in electric fields. Our results show clear evidence that irradiation drives substantial modulation of interfacial electric fields that can be tailored by controlling the atomistic chemical structure of the oxide interface. We show that irradiation can selectively induce built-in electric fields, thereby altering their direction; this suggests a pathway to engineering protective oxide heterostructure overlayers that can electrically control the spatial distribution of defects, with significant implications for the design of corrosion-resistant materials for extreme environments.

Accurate atomistic modeling of screw dislocations in body-centered cubic (BCC) metals remains challenging because their plasticity is governed by complex dislocation glide behavior due to their compact threefold symmetric core structure and a strongly temperature-dependent flow stress induced by the large Peierls barrier. In the context of group 5 (V, Nb, and Ta) and group 6 (Mo and W) refractory metals (RMs), both classical interatomic potentials and some machine-learning potentials consistently fail to reproduce density functional theory (DFT) Peierls barriers and the glide plane. Here, we developed an array of atomic cluster expansion (ACE) potentials for these RMs by extending an existing DFT database. The developed ACE potentials significantly improve the description of screw dislocation properties, showing good agreement with the DFT references for Mo and W and substantial improvement for V, Nb, and Ta. The results show that transferability to screw dislocation behavior depends sensitively on both database composition and element-specific energetics and that achieving a single-humped Peierls barrier alone is not a sufficient validation metric for accurate prediction of dislocation glide. For Nb, Mo, and W, the developed ACE models also enable reliable calculation of kink-pair activation enthalpies, which are well described by both Kocks' law and a line-tension model.

The nonlinear Hall effect (NLHE) provides a powerful probe into the quantum geometry and crystalline symmetry of time-reversal symmetric systems. However, the evolution of its underlying mechanisms across different transport regimes in semiconductors remains a subject of intense debate. In this work, we systematically investigate the NLHE in hydrothermally synthesized $p$-type 2D tellurium (Te) nanoflakes. By implementing oxygen plasma-assisted contact engineering, we achieve high-fidelity signal detection through the suppression of Schottky-barrier-induced artifacts. Our results reveal that the NLHE in Te is governed by extrinsic scattering, as evidenced by a precise quadratic scaling law at temperatures above 30 K. Notably, we identify a remarkable low-temperature scaling anomaly at $T_{\mathrm{R}}\approx 30\mathrm{K}$, where the scaling slope undergoes a dramatic sign reversal, a phenomenon that coincides with the low-temperature transport crossover. Furthermore, thickness-dependent studies show a 3.2-fold enhancement in nonlinear conductance as the flake thickness is reduced to 16 nm, identifying surface-induced symmetry breaking as the primary trigger for activating the nonlinear transport forbidden in the ideal bulk lattice. These findings not only elucidate the scattering-driven origins of NLHE in 2D Te but also establish the effect as a sensitive probe for scattering-mechanism competition and symmetry evolution in chiral semiconductors.

Surface diffusion is the key mass transport process and is commonly described as a Fickian random walk. Using STM and surface diffraction, we show that intercalated Pb under graphene on SiC moves by collective diffusion much faster than random-walk diffusion above a critical coverage ${\theta }_{\mathrm{c}}$ higher than the Pb(111) density. Massive deintercalation of the compressed intercalated layer is observed unexpectedly at room temperature (RT), well below the typical deintercalation temperature of $\sim 550{}^{\circ }\mathrm{C}$. The layer forms after several intercalation/deintercalation cycles, such that its coverage is high, as confirmed by the large drop in the intensity of the diffraction spots. Pb islands with uniform rings at their perimeters that grow at low temperatures are distinctive signatures of collective diffusion ideally studied with STM. LEEM videos of the Pb intercalation reported in the literature further support these nonclassical results.

First-principles calculations are employed to explore avenues to increase the Néel temperature $\left(T_{\mathrm{N}}\right)$ of the magnetoelectric antiferromagnet ${\mathrm{Cr}}_2{\mathrm{O}}_3$ through doping. Employing the hybrid functional method, we calculate the formation energy of intrinsic defects and transition metal dopants (Mo, W, Nb, Ta, Zr, and Hf) to assess their likelihood of formation. Intrinsic defect calculations indicate that Cr interstitials and oxygen vacancies dominate under Cr-rich conditions, whereas Cr vacancies prevail under O-rich conditions. Notably, under Cr-rich conditions, the Fermi level can be pinned slightly above midgap due to the formation of Cr interstitials and oxygen vacancies. Additionally, we identify a split Cr vacancy configuration that is more energetically stable than a normal Cr vacancy in corundum ${\mathrm{Cr}}_2{\mathrm{O}}_3$. To assess the influence of dopants on the $T_{\mathrm{N}}$ of ${\mathrm{Cr}}_2{\mathrm{O}}_3$, we calculate the enhancement of the exchange energy for the spin at the dopant site or at an adjacent Cr site using the supercell method. Our study identifies isovalent Mo and W substitutions at Cr sites as the most promising candidates for increasing the Néel temperature because of impurity-mediated enhancement of the exchange interaction for half-filled bands. Formation-energy calculations indicate that Mo and W substitutions at Cr sites form more readily under Cr-rich conditions and that a Fermi level near or slightly above midgap stabilizes the desirable neutral charge states of the Mo and W defects. This is assisted by the formation of intrinsic Cr interstitials and O vacancies under Cr-rich conditions. These findings offer a route to utilize defects for higher $T_{\mathrm{N}}$ and enhanced performance of ${\mathrm{Cr}}_2{\mathrm{O}}_3$ in magnetoelectric devices and provide useful guidance for future experimental studies.

Epitaxial strain may break the orbital degeneracy, favoring a particular orbital filling. This may influence the magnetic properties of transition metal oxides. Herein, we report the consecutive magnetic order and magnetic anisotropy transitions in $\mathrm{SrM}{\mathrm{n}}_{0.3}{\mathrm{Ir}}_{0.7}{\mathrm{O}}_3$ (SMIO) thin films, with both $3d$ and $5d$ elements on perovskite B sites, as a function of the epitaxial strain. The SMIO films have been epitaxially deposited by pulsed laser deposition on (001)-oriented ${\left({\mathrm{LaAlO}}_3\right)}_{0.3}-{\left({\mathrm{Sr}}_2{\mathrm{AlTaO}}_6\right)}_{0.7}$ substrates buffered with ${\mathrm{BaTiO}}_3$ (BTO) of varying thicknesses. The lattice of the BTO buffer layer relaxes as its thickness increases from 2 to 25 unit cells. Accordingly, the SMIO films deposited epitaxially on top of the BTO buffer layer are subject to a varying strain from compressive to tensile as the BTO thickness increases, driving the SMIO films from antiferromagnetic to ferromagnetic, and then back to antiferromagnetic, accompanied by a change from perpendicular to in-plane magnetic anisotropy. X-ray linear dichroism spectra reveal that the magnetic order and anisotropy in SMIO are associated with the preferential occupation of the Mn $d_{3z^2-r^2}$ or $d_{x^2-y^2}$ orbitals, which is controlled, in turn, by the epitaxial strain.

Epitaxial ${\mathrm{PtCoO}}_2$ thin films were grown on ${\mathrm{Al}}_2{\mathrm{O}}_3\left(0001\right)$ substrates by physical vapor deposition under back-end-of-line compatible conditions, followed by postdeposition annealing to induce crystallization. While annealing-driven structural evolution in delafossite oxides has been reported, the corresponding chemical-state evolution across crystallization and decomposition boundaries remains insufficiently understood. Here, x-ray photoelectron spectroscopy, hard x-ray photoelectron spectroscopy (HAXPES), and in situ x-ray diffraction are combined to track chemical states and phase stability in ${\mathrm{PtCoO}}_2$ thin films as a function of thermal processing. This multimodal approach resolves the spectroscopic fingerprints of the metallic delafossite phase, unambiguously identifying formal $\mathrm{P}{\mathrm{t}}^{1+}$ and $\mathrm{C}{\mathrm{o}}^{3+}$ valence states. Bulk-sensitive HAXPES, reported here for ${\mathrm{PtCoO}}_2$, mitigates surface artifacts and enables direct correlation between bulk chemistry and structural order. Annealing at $800{}^{\circ }\mathrm{C}$ yields phase-pure, epitaxial ${\mathrm{PtCoO}}_2$, whereas higher temperatures induce decomposition into metallic Pt and cobalt oxide phases, defining a narrow thermal stability window. Highly crystalline films down to 4.5 nm thickness exhibit low in-plane resistivities consistent with the metallic delafossite phase. These results establish a chemically specific framework for assessing phase formation and stability in ${\mathrm{PtCoO}}_2$ thin films and demonstrate the utility of combined photoelectron spectroscopy and in situ diffraction for complex oxide metals.

Nb-doped ${\mathrm{TiO}}_2$ has attracted considerable attention due to its potential as a colossal permittivity material. Previous studies suggest that its low-temperature colossal permittivity originates from a low polaron hopping energy barrier, which enables rapid flip-flop migration between neighboring Ti sites. In this work, we employ density functional theory combined with chemical bond analysis to investigate the effects of hydrostatic pressure and uniaxial strain on polaron hopping in pristine rutile ${\mathrm{TiO}}_2$ and Nb-doped ${\mathrm{TiO}}_2$. Under hydrostatic pressure, we find that the hopping energy barrier increases approximately linearly with increasing volume in both systems. This behavior is correlated with pressure-induced modifications of the local Ti environment, which enhance polaron localization. In contrast, uniaxial strain produces a markedly anisotropic response. Pristine ${\mathrm{TiO}}_2$ exhibits the strongest sensitivity when strain is applied along the hopping direction, whereas Nb-doped ${\mathrm{TiO}}_2$ shows saturation of the hopping barrier under compressive strain along the same direction. Our findings highlight the mechanical loading as an effective route to tuning polaron hopping and, consequently, the functional properties of ${\mathrm{TiO}}_2$-based materials.

Understanding how nanocluster cocatalysts modify the electronic structure of III-nitride surfaces is central to the rational design of efficient photocatalytic interfaces. Here, we introduce a region-resolved first-principles framework for analyzing GaN-, InGaN-, and ScGaN-based slabs decorated with six-atom elemental nanoclusters. Using a region-resolved projected local density of states (PLDOS) analysis, we separate the electronic response of nanocluster-covered regions from that of the uncovered semiconductor surface regions, revealing that semiconductor–nanocluster interfaces behave as laterally heterogeneous electronic systems. In this picture, nanocluster-covered regions are associated with local band bending, charge injection, and nanocluster-induced gap states, whereas uncovered nitride regions retain surface-localized states and in-plane dipoles that may influence adsorbate interactions and water-activation pathways. These distinct regional responses motivate the definition of region-resolved interface descriptors, which are further integrated into an Interface Score: a physics-informed comparative metric that combines injection, activation, and interfacial-coupling contributions to rank heterogeneous model interfaces on a common descriptor basis. Machine-learning models trained on global and region-resolved descriptors are used primarily as interpretability tools to assess the descriptors' correlation with single-H adsorption energetics. The results show that spatially averaged descriptors capture broad adsorption-energy trends, while region-resolved descriptors expose complementary local information related to interfacial electrostatics and charge separation. Together, this work establishes a descriptor framework for moving beyond spatially averaged electronic-structure analysis and for bridging first-principles calculations with experimental interpretation of heterogeneous photocatalytic interfaces.

ZnS shows increased flow stresses under light illumination. Although such photoplasticity is considered to be related to changes in dislocation-mobility induced by light, explicit profiles of Peierls potentials for individual glide partial dislocations in ZnS have not been revealed. In this study, ${30}^{\circ }$ Shockley-partial dislocations with Zn and S cores were treated by DFT. Specific Peierls potential profiles of the individual partial dislocations were quantitatively calculated, and the relevant Peierls stresses were evaluated. It was found that the reconstructed partial dislocations induced by light illumination have much larger Peierls stresses than those of the pristine unreconstructed partial dislocations. In particular, the calculated large Peierls stresses of the reconstructed partial dislocations indicate that these dislocations are indeed immobile under light illumination. These results indicate that atomic reconstruction of the partial-dislocation cores caused by photoexcited carriers is a critical factor contributing to the very low dislocation mobility for experimentally observed photoplasticity in ZnS.