Topological effects arising from the Berry curvature lead to intriguing transport signatures in quantum materials. Two such phenomena are the chiral anomaly and nonlinear Hall effect (NLHE). A unified description of these transport regimes requires a quantitative treatment of both band topology and electron scattering. Here, we show accurate predictions of the magnetoresistance in topological semimetals and NLHE in noncentrosymmetric materials by solving the Boltzmann transport equation with electron-phonon ($e$-ph) scattering and Berry curvature computed from first principles. We apply our method to study magnetotransport in a prototypical Weyl semimetal, TaAs, and the NLHE in strained monolayer ${\mathrm{WSe}}_2$, bilayer ${\mathrm{WTe}}_2$, and bulk ${\mathrm{BaMnSb}}_2$. In TaAs, we find a chiral contribution to the magnetoconductance that is positive and increases with magnetic field, consistent with experiments. We show that $e$-ph interactions can significantly modify the Berry curvature dipole and its dependence on temperature and Fermi level, highlighting the interplay of band topology and electronic interactions in nonlinear transport. The computed nonlinear Hall response in ${\mathrm{BaMnSb}}_2$ is in agreement with experiments. By adding the Berry curvature to first-principles transport calculations, our work advances the quantitative analysis of a wide range of linear and nonlinear transport phenomena in quantum materials.

The accuracy of microstructure-based modeling in predicting the mechanical response of particle reinforced aluminum matrix (${\mathrm{SiC}}_{\mathrm{p}}$/Al) composites is primarily determined by the validation of material constitutive parameters. Therefore, the constitutive parameter calibration process and synergistic mechanism of multiphase damage under uniaxial tensile loading in 35 vol.% ${\mathrm{SiC}}_{\mathrm{p}}$/Al composites were systematically investigated through a combined experimental characterization and microstructure-based modeling. Dual-scenarios microstructure-based models of ${\mathrm{SiC}}_{\mathrm{p}}$/Al composites for nanoindentation and uniaxial tension simulations were established based on quantitative morphological statistics obtained from scanning electron microscopy. By integrating linear array nanoindentation testing with microstructure-based inverse finite element analysis, the constitutive parameters for both the matrix and interfacial phases were successfully calibrated, which were subsequently validated through representative volume element (RVE) model for uniaxial tension simulations and experimental verification. Numerical simulations revealed two key findings: (1) The relative accuracy of the elastic modulus in the parameter-calibrated RVE model increased from 38.68% to 87.99% compared to the precalibrated model, while the relative accuracy of tensile strength improved from 81.13% to 98.73%. (2) During damage evolution, initial damage nucleation occurred at particle sharp corner interfaces. Subsequently, cross-phase coupling between matrix shear-induced localized bands and interfacial cracks formed macroscopic fracture bands.

Since the advent of scanning probe microscopy, elemental- and chemical discrimination on heterogeneous surfaces has been a major challenge. This is mainly due to complex contrast mechanisms, which require considerable indirect structural assumptions of tip and surface and related extensive theoretical modeling. Previously, noncontact atomic force microscopy with atomically defined copper oxide tips (CuOx-tips) showed elemental selectivity on even most complex metal-oxide surfaces [Hütner et al., Science 385, 1241, 2024]. Here we report an investigation of an ionic surface, which allows to directly identify the anionic- and cationic sub lattices even on aperiodic surface structures. In line with previous work on metal oxides [Wiesener et al., ACS Nano 18, 21948, 2024], the present results extend chemically selective imaging of CuOx-tips to a new class of heterogeneous materials.

We develop a conserving Keldysh field theory for a moving dislocation represented by a discrete Kanzaki force and coupled to electronic and phononic baths. Within this framework the configurational electron wind force and the electronic drag emerge as the odd and even components of a single retarded stress correlation kernel constructed from the same deformation potential vertex, placing both mechanisms on the same many-body footing as standard transport coefficients. Symmetry of the slip geometry enforces a shear channel theorem in which electronic drag couples only to shear stress, while the electron wind is polar with respect to the Burgers vector, providing a microscopic mechanism for current-induced texture evolution. The formalism yields closed expressions for electronic drag and electron wind in terms of Fermi surface averages of deformation potentials, band velocities, and the screened Kanzaki projector, with no phenomenological relaxation times or adjustable masses. Evaluated from first principles for edge dislocations in face-centered cubic Al and basal dislocations in hexagonal close-packed Zn, these expressions give electronic drag coefficients that are several orders of magnitude smaller than phonon drag throughout the experimentally relevant temperature range, whereas the electron wind produces configurational stresses of order megapascals at current densities $J\sim {10}^8\text{–}{10}^9\mathrm{A}{\mathrm{m}}^{-2}$, consistent with reported electroplastic softening. Extension to finite magnetic field predicts a magnetoplastic analog of magnetoresistance, in which the drag is suppressed by cyclotron deflection while the wind remains essentially field independent. The theory therefore converts wind and drag from phenomenological fit parameters into parameter free functionals of the electronic structure and provides a direct route from electronic structure calculations to dislocation mobility laws in electroplastic and magnetoplastic flow.

The layered rare-earth diantimonides, $R{\mathrm{Sb}}_2$, ($R$ = lanthanide element) composed of Sb square-net sheets exhibit diverse structural phases with distinct stacking configurations which can be tuned by the growth temperature, stoichiometry, and pressure. The recent discovery by Llanos et al. [Nano Lett. 24, 8518 (2024)] of a novel monoclinic polymorph of ${\mathrm{LaSb}}_2$ raises the important question as to why ${\mathrm{LaSb}}_2$ has been synthesized in the orthorhombic phase in previous experimental studies. We have employed first-principles electronic structure calculations to investigate the effect of charge doping and phonon entropy on the relative stability between four competing structural phases of ${\mathrm{LaSb}}_2$: the ${\mathrm{SmSb}}_2$-type, the ${\mathrm{YbSb}}_2$-type, the MBE-grown monoclinic, and our novel theoretically predicted orthorhombic structures (space group No. 58, $Pnnm$). The calculations reveal that the ${\mathrm{SmSb}}_2$-type orthorhombic phase is stabilized by electron doping that can presumably occur during bulk growth conditions such as Sb-rich flux, intrinsic vacancy formation, etc. However, the phonon entropy is found to reduce the free energy of the monoclinic phase faster than that of the orthorhombic phase with increasing temperature, indicating that the monoclinic phase becomes more stable at high temperatures. We also present the dynamical instabilities in two well-known structures with or without strain that qualitatively explain the pressure-dependent charge density waves of ${\mathrm{LaSb}}_2$. This research aims to shed light on the microscopic mechanisms underlying the complex and competing structural phases and resulting transitions in the family of $R{\mathrm{Sb}}_2$ systems.

Electron-irradiation induced creep rates in amorphous alloys, a-${\mathrm{SiO}}_2, {\mathrm{Fe}}_{79}{\mathrm{B}}_{16}{\mathrm{Si}}_5, {\mathrm{Cu}}_{60}{\mathrm{Ta}}_{40}$, and ${\mathrm{Cu}}_{50}{\mathrm{Ti}}_{50}$, were measured at room temperature using a miniaturized beam-bending apparatus within a transmission electron microscope operated at 200 keV. The creep rates of these amorphous samples increased nearly linearly with both e-beam current density and applied stress, while a reference crystalline (c-)${\mathrm{SiO}}_2$ sample failed to creep under the same conditions. The irradiation-induced creep compliance of a-${\mathrm{SiO}}_2$ was $\sim 15$ times larger than that of ${\mathrm{Fe}}_{79}{\mathrm{B}}_{16}{\mathrm{Si}}_5$ and over 1,000 times larger than that of the two Cu alloys. Molecular dynamics computer simulations were employed to simulate electron irradiation induced creep using interatomic potentials representing amorphous ${\mathrm{Cu}}_{75}{\mathrm{Zr}}_{25}, {\mathrm{Ni}}_{85}{\mathrm{P}}_{15}$, and ${\mathrm{SiO}}_2$ as model systems. The irradiation induced creep compliances calculated for ${\mathrm{Cu}}_{75}{\mathrm{Zr}}_{25}$ during 200 keV electron irradiation provided good quantitative agreement with the two Cu-based alloys, but that for a-${\mathrm{SiO}}_2$ was $\sim 180$ times too small. These results indicate that unlike neutron or ion-beam induced creep in a-${\mathrm{SiO}}_2$, creep under electron irradiation is dominated by the effects of ionization, owing largely to the far higher ratio of electronic stopping to nuclear stopping for electrons than for ions.

Defect engineering and functionalization enable the precise modulation of a material's local reactivity, electronic doping, and optical response. Motivated by its promising optical and excitonic characteristics, we show that the electronic properties of the 2H-phase ${\mathrm{TiBr}}_2$ monolayer can be effectively tuned via vacancy engineering and adatom functionalization, thereby unlocking potential applications in catalysis, sensing, and optoelectronic devices. Herein, using density functional theory (DFT), we investigate pristine (${\mathrm{TiBr}}_2^{\text{pri}}$) and its modified monolayers by including vacancies Br-type (${\mathrm{TiBr}}_2^{\text{vac}}$), as well as those functionalized by common atomic adsorbates (X = H, C, N, and O, denoted as $\mathrm{X}/{\mathrm{TiBr}}_2$). For the pristine surface, all adatoms exhibit weak physisorption, with adsorption energies $|E_{\text{ads}}| < 1\mathrm{e}\mathrm{V}$. In contrast, the introduction of Br vacancies dramatically enhances the surface reactivity, resulting in strong chemisorption at the vacancy sites (for all adatoms) with large adsorption energies and substantial electronic modifications. The present work provides a comprehensive energetic decomposition framework (adsorption, interaction, and distortion energies) applied to transition-metal dihalide monolayers. We expect that similar defect- and adatom-induced reactivity may emerge in structurally related 2D transition-metal halides. In addition, our findings demonstrate that the electronic and adsorptive properties of ${\mathrm{TiBr}}_2$ monolayers can be rationally engineered through defect and adatom manipulation.

Lattice vacancy migration barriers in ferromagnetic ${\mathrm{Fe}}_x{\mathrm{Ni}}_{1-x}$ alloys ($0.4\le x\le 0.6$) are accurately quantified within the framework of ab initio electronic structure calculations using the nudged elastic band (NEB) method. Both the atomically disordered (A1) fcc phase, as well as the atomically ordered, tetragonal $\mathrm{L}{1}_0$ phase—which is under consideration as a material for a rare-earth-free gap magnet for advanced engineering applications—are investigated. Across an ensemble of NEB calculations performed on supercell configurations spanning a range of compositions and containing disordered, partially ordered, and fully ordered structures, we find that Ni-vacancy interchanges encounter significantly higher energetic barriers than do Fe-vacancy interchanges. We contend that this aspect is a key factor in determining the differences in mobility between Fe and Ni atoms in this ferromagnetic alloy. Moreover, we are able to interpret these findings in terms of the ferromagnetic alloy's underlying spin-polarized electronic structure. Specifically, we report a coupling between the size of local lattice distortions and the magnitude of the local electronic spin polarization around vacancies. This causes Fe atoms to relax into lattice vacancies, while Ni atoms remain rigidly fixed to their original lattice positions. These results give atomic-scale insight into the longstanding experimental observation that Ni exhibits remarkably slow atomic diffusion in Fe-Ni alloys.

Harnessing nonlinear interactions between phonon modes in condensed matter presents a powerful avenue for tailoring material properties for innovative applications in future information devices. Here we report a study of nonlinear coupling between infrared (IR) active and Raman-active phonon modes in rare-earth orthoferrites $\mathrm{ErFe}{\mathrm{O}}_3, \mathrm{TmFe}{\mathrm{O}}_3$, and $\mathrm{TbFe}{\mathrm{O}}_3$. To reveal the nonlinear phonon interactions, we resonantly excite IR-active phonons with an ultrashort midinfrared pulse, with its central wavelength tunable in the 3–18 µm (16.5–100 THz) range, and trace the phonon modes in the time domain after the excitation. We identify two main coupling mechanisms: quadratic linear and trilinear, which stand for a nonlinear coupling of the Raman-active phonon with either one or two distinct IR-active modes, respectively. The origin of driving each Raman-active phonon mode is identified and analyzed with polarization-dependent pump-probe spectroscopy. Our results show a strong dependence of the trilinear coupling mechanism on the crystallographic orientation of the sample, thus revealing that only specific phonon modes can exhibit this coupling.

The native surface oxide of plutonium plays a critical role in ensuring the stability and safe storage of the underlying metal; consequently, understanding the role of defects and impurities in determining the properties of the oxide layer is critical. Here, we use hybrid density-functional theory calculations to evaluate the electronic structure and defect chemistry of ${\mathrm{PuO}}_2$, the most stable of the native oxide phases, including both native and extrinsic defects. We find that oxygen vacancies ($V_{\mathrm{O}}$) form readily in ${\mathrm{PuO}}_2$, as do polarons. Electron polarons (${\eta }^{-}$) are the lowest-energy acceptor species in ${\mathrm{PuO}}_2$, while the charge compensating donor species will shift from $V_{\mathrm{O}}$ under O-poor conditions to hole polarons (${\eta }^{+}$) under O-rich conditions. Nitrogen and fluorine can substitute readily for oxygen atoms under O-poor conditions, while fluorine can also incorporate in an interstitial configuration (${\mathrm{F}}_i^{-}$) under more O-rich conditions. Carbon and chlorine incorporation in ${\mathrm{PuO}}_2$ will be very limited. We also evaluate the kinetic barriers for oxygen-related defects, which we find to diffuse readily when present. Our results provide valuable insights into the critical role and variable chemistry of point defects and impurities in ${\mathrm{PuO}}_2$, which in turn have important implications for the safe storage of the underlying metal layer. In short, exposure of freshly prepared plutonium to reactive nitrogen- and fluorine-containing contaminants should be avoided, while carbon- or chlorine-containing contaminants are less likely to incorporate readily into the oxide.

In this work, we simulate the spectral emissivity of various stoichiometric crystal phases of ${\mathrm{Mo}}_x{\mathrm{Si}}_y$ compounds using density functional perturbation theory. The dielectric function, including electronic and ionic contributions, is calculated for each phase. We use the bulk properties obtained to simulate the optical absorption spectrum originating from the compound in thin film ($\sim 20\mathrm{nm}$) form. We find that most thin films of ${\mathrm{Mo}}_x{\mathrm{Si}}_y$ are metallic, however, our results indicate that their emissivity is not simply correlated with the Mo content. For hot metallic films at around 900 K, we predict a maximal emissivity between 5–10 nm thickness. Our results are in good qualitative agreement with experiments, confirming that the emissivity of hexagonal ${\mathrm{MoSi}}_2$ is much lower than in the tetragonal phase. This is related to the small band gap (hexagonal ${\mathrm{MoSi}}_2$) and low density of states at the Fermi level (tetragonal ${\mathrm{MoSi}}_2$). Furthermore, test calculations on defected ${\mathrm{MoSi}}_2$ demonstrate that the infrared emissivity of ${\mathrm{MoSi}}_2$ thin films can be substantially increased by introducing defects.

We present an in-depth study of electronic transport in atomic-sized gold contacts using Break-Junction (BJ) techniques under cryogenic and ambient conditions. Our experimental results, supported by classical molecular dynamics (CMD) simulations and ab initio calculations, provide compelling evidence for the formation of three-atom-thick structures in gold nanocontacts under tensile stress. These findings extend previous studies that confirmed the existence of one- and two-atom-thick chains. Beyond identifying these novel atomic configurations, we introduce a fast and robust calibration method for Break-Junction systems, leveraging the characteristic length of these structures to convert piezo-distance into absolute distance in angstroms. Our approach presents a novel and robust method for calibrating atomic distances in atomic conductor systems at both cryogenic and room temperatures. The results also enable the assessment of electrode sharpness, even under ambient conditions.

Accurately predicting the crack behavior of magnesium-lithium (Mg-Li) alloys through atomic-scale simulations is essential for understanding crack-defect interactions and designing high-plasticity alloys. However, existing molecular dynamics potentials for Mg-Li alloys are inadequate for reliably modeling crack-related phenomena, such as stacking fault energies and dislocation core structures. In this work, by combining 1722 density functional theory (DFT) calculated data points with machine learning method, we develop a broadly applicable machine learning potential (MLP) for Mg-Li alloys. This MLP accurately reproduces lattice constants, elastic constants, surface energies, and generalized stacking fault energy curves, showing reasonable agreement with DFT data. Furthermore, MLP simulations reveal that either the continuous formation of basal ${\mathrm{I}}_2$ stacking faults or the formation of basal ${\mathrm{I}}_1$ stacking faults trigged by the cross-slip of pyramidal dislocation effectively relieves stress concentration at the crack tip, resulting in crack blunting. These findings help clarify the experimental debate regarding the dual role of basal slip: basal slip bands can also delay crack propagation, while discontinuous basal slip can initiate fatigue cracks.

We present a study of low-temperature electric and thermal transport in ${\mathrm{RuO}}_2$, a metallic oxide which has attracted much recent attention. Careful scrutiny of electric resistivity reveals a quadratic temperature dependence below $\sim 20$ K undetected in previous studies of electronic transport in this material. The prefactor of this $T^2$ resistivity, given the electronic specific heat, corresponds to what is expected by the Kadowaki-Woods scaling. The variation of its amplitude across four different samples is negligible despite an eightfold variation of residual resistivity. There is also a $T^5$ resistivity due to scattering by phonons. By measuring thermal conductivity $\kappa$ at zero field and at 12 T, we separate its electronic and phononic components and find that the former respects the Wiedemann-Franz law at zero temperature and deviates downward at finite temperature. The latter corresponds to a threefold discrepancy between the prefactors of the two (thermal and electric) $T$-square resistivities. Our results, establishing ${\mathrm{RuO}}_2$ as a weakly correlated Fermi liquid, provide input for the ongoing theoretical attempt to give a quantitative account of electron-electron scattering in metallic oxides starting from first principles.

Bulk boron phases are typically insulating due to sufficiently localized valence electrons, so that stable metallic boron phases at ambient conditions are rare. This situation is further exacerbated by the limited understanding of mechanism governing electronic properties of boron phases. Here, we report a series of stable metallic and insulating boron phases at ambient pressure, identified by an extensive structural search combining graph theory, group theory-based random strategies, and global optimization algorithms. Among these, an R3c-symmetry phase (${\mathrm{B}}_{\text{R}3\mathrm{c}}$), composed of six ${\mathrm{B}}_9$ structural units, exhibits exceptional thermal stability up to 1200 K, a Vickers hardness exceeding 40 GPa, and higher thermodynamic stability than the experimentally known ε-B phase by 0.11 eV/atom. First-principles analysis reveals that the ${\mathrm{B}}_{\text{R}3\mathrm{c}}$ metallicity stems from delocalized electronic states by uniform B-B bond lengths and high-coordinate number. Motivated by this, we develop a physically interpretable one-dimensional descriptor based on the bond topology and electron localization parameters, which can correctly predict 95.1% of all reported metallic or insulating boron phases. These results constitute a predictive framework for designing boron and boron-based functional materials.