ZnS is a brittle material but shows extraordinary plasticity during mechanical tests performed in complete darkness. This phenomenon is known as the photoplastic effect, whose underlying mechanisms have long been unclear. We study the impact of light, via photoexcited charge carriers, on the dislocation core structure and mobility using first-principles calculations. We calculate the core structure and the charge-dependent Peierls barriers of the glide set of Shockley partial dislocations in ZnS. Our findings reveal that locally charged dislocations capture excess carriers in the system, leading to core reconstructions that alter the Peierls barrier, resulting in higher barriers and lower mobility for these dislocations. This altered and asymmetric mobility, depending on dislocation character (edge or mixed) and local stoichiometry (Zn or S rich), is responsible for the brittle behavior of ZnS under light exposure and will be reversed in complete darkness.

The accurate treatment of electronic effects in multi-million-atom simulations of radiation-induced collision cascades is crucial for reliable predictions of primary radiation damage. In this work, we explore the fidelity of a recently developed two-temperature molecular dynamics model implementing an electron density-dependent coupling of electronic and atomic subsystems for cascade simulations in nickel. We show that the parameter-free model realistically captures the instantaneous energy losses during all stages of the highly nonequilibrium cascade process. Our simulations predict two distinct coupling regimes, corresponding to the rapid energy losses through electronic stopping in the early stages of the cascade and to the slow equilibration through the electron-phonon coupling mechanism in the later stages, without the use of separate models or coupling terms. The intermediate stage of the cascade dynamics displays a complex energy transfer between the subsystems, which cannot be interpreted by comparison to either electronic stopping or electron-phonon coupling theories. We therefore compare the predicted atomic mixing, which is sensitive to the energy losses during the intermediate cascade stage, with experimental ion beam mixing measurements. We find good agreement with the experiments, validating the coupling model for the intermediate stage of the cascade. Predictions of final defect numbers and cluster sizes are found in line with the results from conventional electronic stopping-based methods, while significantly reducing the theoretical uncertainty in the outcomes of conventional models stemming from arbitrary choices of thresholds for different coupling terms. Our results represent a notable improvement in cascade damage predictions in nickel, providing validation of the electron density-dependent coupling model for radiation damage simulations in general. The results lead us to propose an interpretation of the electronic energy losses in the intermediate regime of velocities, where we find an effectively nonlinear dissipation.

Ferrimagnetic semiconductors, integrated with net magnetization, antiferromagnetic coupling, and semiconducting nature, comprise an ideal platform for spintronics. For practical applications, achieving high Néel temperatures ($T_{\mathrm{N}}$) is very desirable but remains a significant challenge. Here, via high-throughput density functional theory calculations, we identify 19 intrinsic ferrimagnetic semiconductor candidates from nearly 44 000 structures in the Materials Project database, including 10 ferrimagnetic bipolar magnetic semiconductors (BMSs) and 9 ferrimagnetic half semiconductors (HSCs). Notably, the BMS ${\mathrm{NaFe}}_5{\mathrm{O}}_8$ possesses a high $T_{\mathrm{N}}$ of 768 K. By element substitutions, we obtain an HSC ${\mathrm{NaFe}}_5{\mathrm{S}}_8$ with a $T_{\mathrm{N}}$ of 957 K and a BMS ${\mathrm{LiFe}}_5{\mathrm{O}}_8$ with a $T_{\mathrm{N}}$ reaching 1059 K. Our results pave a promising avenue toward the development of ferrimagnetic spintronics at ambient temperature.

Bismuth (Bi) films hold potential for spintronic devices due to strong spin-orbit coupling. Understanding the growth, surface states, and interactions with the substrate is key to their functionalization. Large-area high-quality (111) Bi ultrathin films were grown on InSb (111)B substrates by molecular beam epitaxy (MBE). Strong film-substrate interactions epitaxially stabilize the (111) orientation and lead to nonequivalent interface potentials. Analysis of angle-resolved photoemission spectroscopy (ARPES) measurements, employed to characterize the evolution of the surface states with film thickness, indicate a crossing at the $\overline{M}$ point, suggesting a topologically trivial phase in the thin film. The results show the presence of interfacial bonds to the substrate breaks inversion symmetry, preventing the semimetal-to-semiconductor transition predicted for freestanding bismuth layers, highlighting the importance of controlled functionalization and surface passivation of two-dimensional materials.

Recent advances in experimental techniques and computational methods have significantly expanded the family of alkali antimonides, a class of semiconducting materials used as photocathodes in particle accelerators, unveiling new crystal structures and stoichiometries with improved stability and quantum efficiency. This work investigates the electronic and optical properties of eight Na- and K-based alkali antimonide binary crystals with 3:1 and 1:1 alkali-to-antimony ratios, which were predicted to be stable in a recent high-throughput screening study. Employing density functional theory and many-body perturbation theory, we find that all systems exhibit direct band gaps, except for monoclinic ${\mathrm{Na}}_8{\mathrm{Sb}}_8$, which has a nearly degenerate indirect gap. Optical spectra are characterized by near-infrared absorption onsets and intense visible excitations. Our analysis highlights the significant role of electron-hole correlations, particularly in K-based compounds, leading to exciton binding energies above 100 meV and sharper absorption peaks. In-depth inspection of the electronic contributions to the excited states provides additional insight into the role of excitonic effects. By shedding light on the fundamental properties of alkali antimonide binary crystals, our results are relevant for the design and optimization of next-generation electron sources for particle accelerators.

Ferrimagnets, in which half the spins are disordered and half are ordered—the so-called half-fire, half-ice state—have been advanced theoretically as a route towards realizing exotic magnetic ground states. Here we demonstrate novel single-spin resonance in $\mathrm{SmM}{\mathrm{n}}_2\mathrm{G}{\mathrm{e}}_2$, a 1/3-fire, 2/3-ice material. Using ac susceptibility in the frequency range 0.1 Hz–1 kHz we find a Debye-like resonance with Orbach relaxation temperature dependence, yielding an energy barrier $E_B\approx 840k_B$ and attempt frequencies in the THz range. These quantities strongly suggest single-spin relaxation among paramagnetic Sm spins where the flipping field is provided by the ferromagnetically-ordered Mn spins at domain boundaries, a direct outcome of the 1/3-fire, 2/3-ice state.

Interfacial energy plays a crucial role for high-temperature material systems in determining their microstructure evolution and mechanical properties. Optimizing the interfacial energy through doping can improve the stability, performance, and overall functionality of these materials. The present study delivers theoretical investigation on the sigma FeCr (001)//FCC Fe (111) interfacial energy using ab initio methods, focusing on the implications of interfacial doping with important interstitial elements carbon (C), boron (B), and nitrogen (N). The calculated interfacial energy without doping is $0.183\mathrm{J}/{\mathrm{m}}^2$. Upon doping, notable reductions in interfacial energy were observed. Doping with B decreased the interfacial energy to $0.046\mathrm{J}/{\mathrm{m}}^2$, with single C doping to $0.126\mathrm{J}/{\mathrm{m}}^2$, with two C doping to $0.098\mathrm{J}/{\mathrm{m}}^2$, and with a single N doping to $0.071\mathrm{J}/{\mathrm{m}}^2$. These findings not only shed light on the atomistic origin for the effect of stabilizing the microstructure of stainless steel at elevated temperatures by interstitial doping, but also present a systematic, thorough ab initio approach to predict interfacial doping properties and guide alloy design to enhance the performance and stability.

Lead-based perovskite solar cells have reached high efficiencies, but toxicity and lack of stability hinder their wide-scale adoption. These issues have been partially addressed through compositional engineering of perovskite materials, but the vast complexity of the perovskite materials space poses a significant obstacle to exploration. We previously demonstrated how machine learning (ML) can accelerate property predictions for the $\mathrm{CsPb}{(\mathrm{Cl}/\mathrm{Br})}_3$ perovskite alloy. However, the substantial computational demand of density functional theory (DFT) calculations required for model training prevents applications to more complex materials. Here, we introduce a data-efficient scheme to facilitate model training, validated initially on $\mathrm{CsPb}{(\mathrm{Cl}/\mathrm{Br})}_3$ data and extended to the ternary alloy $\mathrm{CsSn}{(\mathrm{Cl}/\mathrm{Br}/\mathrm{I})}_3$. Our approach employs clustering to construct a compact yet diverse initial dataset of atomic structures. We then apply a two-stage active learning approach to first improve the reliability of the ML-based structure relaxations and then refine accuracy near equilibrium structures. Tests for $\mathrm{CsPb}{(\mathrm{Cl}/\mathrm{Br})}_3$ demonstrate that our scheme reduces the number of required DFT calculations during the different parts of our proposed model training method by up to 20% and 50%. The fitted model for $\mathrm{CsSn}{(\mathrm{Cl}/\mathrm{Br}/\mathrm{I})}_3$ is robust and highly accurate, evidenced by the convergence of all ML-based structure relaxations in our tests and an average relaxation error of only 0.5 meV/atom.

The discovery of novel quantum materials within ternary phase spaces containing antagonistic pairs such as Fe with Bi, Pb, In, and Ag, presents significant challenges yet holds great potential. In this work, we investigate the stabilization of these immiscible pairs through the integration of Cerium (Ce), an abundant rare-earth and cost-effective element. By employing a machine learning (ML)-guided framework, particularly crystal graph convolutional neural networks (CGCNN), combined with first-principles calculations, we efficiently explore the composition/structure space and predict 9 stable and 37 metastable Ce-Fe-X $(\mathrm{X}=\mathrm{Bi}, \mathrm{Pb}, \mathrm{In}, \text{and} \mathrm{Ag})$ ternary compounds. Our findings include the identification of multiple new stable and metastable phases, which are evaluated for their structural and energetic properties. These discoveries not only contribute to the advancement of quantum materials but also offer viable alternatives to critical rare earth elements, underscoring the importance of Ce-based intermetallic compounds in technological applications.

Sliding ferroelectricity in two-dimensional materials, characterized by reversible polarization due to the relative sliding of adjacent layers, has uncovered a new era of advancement in data storage and nonvolatile memory devices. A recent experimental study on intralayer sliding of GaSe has illustrated the possibility of a distorted Q phase, which is capable of inducing switchable polarization at the monolayer limit. In this study, we use first-principles calculations based on density functional theory to further investigate the stability of the Q phase by analyzing a full energy landscape of intralayer sliding under equilibrium conditions and under the influence of external factors such as strain, electric field, and doping. No indication of a metastable state is found near the distorted Q phase. We extend our investigation to interlayer sliding of bilayer and bulk GaSe and associated polarization-switching energy barriers. The spontaneous ferroelectric polarization flips between $\pm 0.19\mu {\mathrm{C}\mathrm{cm}}^{-2}$ in the out-of-plane direction for bulk GaSe along the interlayer sliding trajectory. This study provides significant insight into the future progression of slidetronics and the enhancement of ferroelectric technologies.

The local electronic structure of the metal active site often dominates the molecular adsorption on single-atom catalysts (SACs), a key process for understanding the catalytic mechanism. Herein, using constant-potential method, we delve into the role of the substrate's electronic structure in molecular adsorption on metal-embedded nitrogen-doped graphene (M-N-C) SACs under electrochemical potential. Using ${\mathrm{O}}_2$ as a model adsorbate and ${\mathrm{FeN}}_4$ and ${\mathrm{FeNC}}_3$ as model SACs, we observe a decrease in ${\mathrm{O}}_2$ adsorption strength with increasing electric potential on ${\mathrm{FeN}}_4$. This behavior is primarily due to changes in the electronic structure of the ${\mathrm{FeN}}_4$ substrate upon ${\mathrm{O}}_2$ adsorption, which causes a downward shift in the Fermi level and, consequently, an upward shift in the potential of zero charge. This shift leads to different responses in the total energy of ${\mathrm{FeN}}_4$ with and without ${\mathrm{O}}_2$ adsorption under applied potential. Further, we find that the ${\mathrm{O}}_2$ adsorption energy difference between ${\mathrm{FeN}}_4$ and ${\mathrm{FeNC}}_3$ follows a quadratic dependence on electric potential, with the parabola's opening controlled by the quantum capacitance difference between ${\mathrm{FeN}}_4$ and ${\mathrm{FeNC}}_3$ with adsorbed ${\mathrm{O}}_2$ . Notably, the electronic states responsible for this difference are distributed across the entire Fe-N-C SACs plane, highlighting again the critical role of the substrate's electronic structure in modulating ${\mathrm{O}}_2$ adsorption. This paper underscores the significant role of the substrate's electronic structure for molecular adsorption on the metal active center of SACs, enhancing the understanding of fundamental molecule-catalyst interactions under electrochemical potential.

The investigation of topological materials has uncovered groundbreaking phases of matter with significant implications for quantum technologies. Here, we explore the antiferromagnetic topological insulator family $\mathrm{V}{\left({\mathrm{Bi}}_{1-x}{\mathrm{Sb}}_x\right)}_2{\mathrm{Te}}_4$ ($x=0, 0.5$, 1), formed by introducing vanadium telluride layers into the layered topological insulator (${\mathrm{Bi}}_{1-x}{\mathrm{Sb}}_x{)}_2{\mathrm{Te}}_3$. Our results reveal the tunability of the spin Hall conductivity and its topological contribution, quantified by the recently introduced average spin Chern number, via Sb concentration. The materials' strong topological insulating behavior is established through spin-orbit-coupling-induced band inversions, nontrivial ${\mathbb{Z}}_2$ invariants, and the presence of topological surface states. These findings position $\mathrm{V}{\left({\mathrm{Bi}}_{1-x}{\mathrm{Sb}}_x\right)}_2{\mathrm{Te}}_4$ as promising candidates for next-generation spintronic devices and advanced quantum applications.

Magnetoelectric multiferroic semiconductors offer great promise for applications in magnetic storage, optoelectronics, and advanced spintronics. These materials require strong magnetization, polarization, a moderate energy gap ($1.5\text{eV}<E_g<3\text{eV}$), and high transition temperatures for both ferroelectric and ferromagnetic properties. This paper investigates six double perovskite oxides (DPOs), ${AA}^{\prime }{\mathrm{FeOsO}}_6$ ($A$ = Na, K, Rb; $A^{\prime }$= La, Y), as potential candidates. We used density functional theory to find that DPOs exhibit a polar $\mathrm{P}{2}_1$ phase with an $a^{-}{a}^{-}{c}^{+}$ tilt pattern. The polarization results from the noncancellation of layered polarization between $A\mathrm{O}$ and $A^{\prime }\mathrm{O}$ layers, which can be switched by altering their relative displacement. The strong antiferromagnetic coupling between ${\mathrm{Fe}}^{3+}$ ($S$ = 5/2) and ${\mathrm{Os}}^{5+}$ ($S$ = 3/2) leads to a stable ferrimagnetic ground state. These materials demonstrate semiconducting properties with a band gap $E_g<$ 3 eV and strong absorption in both the visible and ultraviolet regions. Ab initio molecular dynamics simulations show that the ferroelectric polarization switching temperatures exceed 300 K, making these materials suitable for room-temperature applications.

We report on molecular-dynamics simulations of the atomic structure and diffusion processes at Al(110)/Si(001) interphase boundary created by simulated vapor deposition of Al(Si) alloy onto Si(001) substrate. An array of parallel misfit dislocations of both full and partial types is observed at the interface. Si atoms segregate to the misfit dislocations, with segregation to full dislocations being stronger. The interface diffusion is dominated by short-circuit diffusion along the misfit dislocations, creating a significant diffusion anisotropy. Diffusion of Al and Si atoms along the full misfit dislocations is faster than along the partial-misfit dislocations. Due to the presence of the misfit dislocations, diffusion at the Al(110)/Si(001) interface studied here is faster than diffusion at the Al(111)/Si(111) interfaces investigated in our previous work.

Two-phase heterogeneous materials arising in a variety of natural and synthetic situations exhibit a wide variety of microstructures and thus display a broad spectrum of effective physical properties. Given that such properties of disordered materials generally depend on an infinite set of microstructural correlation functions that are typically unobtainable, in practice, theoretical approaches must rely on rigorous bounds and approximations on the effective properties that depend on a limited set of nontrivial microstructural information. Torquato [Random Heterogeneous Materials, Microstructure and Macroscopic Properties (Springer-Verlag, New York, 2002)] derived such an approximation for the effective thermal/electrical conductivity of two-phase microstructures that perturb about those that realize the well-known self-consistent formula, a key feature of such microstructures being phase-inversion symmetry which can be observed in certain cellular, bicontinuous, and porous materials. Here, we show via extensive numerical simulations that this virtually unexamined approximation, which depends on up to three-point correlations functions, accurately predicts the effective conductivities of various two- and three-dimensional two-phase microstructures across phase volume fractions in which both phases can form large and well-connected clusters, including certain phase-inversion symmetric microstructures as well as phase-inversion asymmetric dispersions of certain fully penetrable particles. We also highlight the accurate sensitivity of this approximation to phase-connectedness properties by showing that it predicts percolation thresholds that are in good quantitative and/or qualitative agreement with known thresholds for the models considered here. Finally, we discuss how this formula can be used to design materials with desirable effective conductivity properties and thus aid in materials by design.

${\mathrm{Bi}}_2{\mathrm{O}}_2\mathrm{Se}$ belongs to a group of quasi-2D semiconductors that can replace silicon in future high-speed/low-power electronics. However, the correlation between crystal/band structure and other physical properties still eludes understanding: carrier mobility increases non-intuitively with carrier concentration; the observed ${\mathrm{T}}^2$ temperature dependence of resistivity lacks explanation. Moreover, a very high relative out-of-plane permittivity of about 150 has been reported in the literature. A proper explanation for such a high permittivity is still lacking. We have performed infrared (IR) reflectivity and Raman scattering experiments on a large perfect single crystal with defined mosaicity, carrier concentration, and mobility. Five of the eight phonons allowed by factor group theory have been observed and their symmetries determined. The IR spectra show that the permittivity measured in the tetragonal plane is as high as ${\varepsilon }_r\approx 500$, and this high value is due to a strong polar phonon with a low frequency of ∼34 ${\mathrm{cm}}^{-1}$ (∼1 THz). Such an unusually high permittivity allows the screening of charge defects, leading to the observation of high electron mobility at low temperatures. It also allows effective modulation doping providing a platform for high-performance 2D electronics. DFT calculations suggest the existence of a very low-frequency acoustic phonon ∼14 ${\mathrm{cm}}^{-1}$ (∼0.4 THz). Both the low-frequency phonons cause anomalous phonon DOS, which is reflected in the unconventional temperature dependence of the heat capacity, $C_p\approx {\mathrm{T}}^{3.5}$. The temperature-dependent, two-component group velocity is proposed to explain the unusual temperature dependence of the thermal conductivity, $\kappa \approx {\mathrm{T}}^{1.5}$.

Accurate predictions of the properties of transition-metal oxides using density functional theory (DFT) calculations are essential for the computational design of energy materials. In this work, we investigate the anomalous reversal of the stability of structural distortions (where distorted structures go from being energetically favorable to sharply unfavorable relative to undistorted ones) induced by $\mathrm{DFT}+U_{\text{eff}}$ on Mo d orbitals in layered $A{\mathrm{MoO}}_2$ $(A=\mathrm{Li}, \mathrm{Na}, \mathrm{K})$ and rutilelike ${\mathrm{MoO}}_2$. We highlight the significant impact of varying $U_{\text{eff}}$ values on the structural stability, convex hull, and thermodynamic stability predictions, noting that deviations can reach up to the order of 100 meV/atom across these energetic quantities. We find the transitions in stability are coincident with changes in the electron localization, magnetic behavior, and volume. The anomalous reversal persists across PBE, ${\mathrm{r}}^2\mathrm{SCAN}$ functionals, and also with vdW-dispersion energy corrections $(\mathrm{PBE}+\mathrm{D}3)$. In Mo-containing oxide systems, high $U_{\text{eff}}$ leads to inaccurate descriptions of physical quantities and structural relaxations under artificial symmetry constraints, as demonstrated by the phonon band structures, the Heyd-Scuseria-Ernzerhof hybrid functional results, and comparisons with experimental structural data. We conclude that high $U_{\text{eff}}$ values (around 4 eV and above, depending on the specific structures and compositions) might be unsuitable for energetic predictions in A-Mo-O chemical spaces. Our results suggest that the common practice of applying $\mathrm{DFT}+U_{\text{eff}}$ to convex hull constructions, especially with high $U_{\text{eff}}$ values derived from fittings, should be carefully evaluated to ensure that ground states are correctly reproduced, with careful consideration of dynamic stability and possible energetically favorable distortions.