$\text{G}{\text{a}}_2{\text{O}}_3$/GaAs heterojunctions are emerging as promising candidates for next-generation power electronics, photonics, and energy devices, leveraging the high breakdown voltage and thermal stability of $\text{G}{\text{a}}_2{\text{O}}_3$ alongside the mature technology, high hole mobility, and high refractive index of GaAs. The efficiency of these devices depends strongly on the band alignment between the two materials, however both type-I and type-II alignment have been reported in the literature for these heterostructures. To address this ambiguity, we use hybrid density functional theory to systematically investigate the band alignment at GaAs/$\text{G}{\text{a}}_2{\text{O}}_3$ interfaces, focusing on the role of interface chemistry. By considering Ga-O-, As-, and As-O-rich interfaces both in amorphous and crystalline $\text{G}{\text{a}}_2{\text{O}}_3$ phases, we demonstrate that interface stoichiometry determines the alignment type: Ga-O-rich interfaces exhibit type-II alignment with large valence band offsets (∼3.1 eV), while As-rich and As-O-rich interfaces favor type-I alignment with reduced offsets (∼2.3–2.6 eV). These trends are attributed to interface dipole formation driven by bonding configuration. Our findings provide insight into the relationship between chemistry and band alignment in GaAs/$\text{G}{\text{a}}_2{\text{O}}_3$ heterostructures, enabling targeted optimization for specific device applications.

The recently investigated nitrogen (N) incorporation into TiNbMoTaW high entropy alloy films leads to a domelike superconducting transition temperature $T_C$ vs nitrogen concentration $x$ (with $x=\text{N}/M$ representing the ratio between atomic fractions of nitrogen and metal atoms, $M=\mathrm{Ti}+\mathrm{Nb}+\mathrm{Mo}+\mathrm{Ta}+\mathrm{W}$) in the respective high entropy nitride ${\left(\mathrm{TiNbMoTaW}\right)}_{1.0}{\mathrm{N}}_x$, with a large $T_C$ enhancement. In this study, we report on the effect of N insertion into NbTaHfTiZr films, which show a lower valence electron concentration and a lower configuration entropy than those of TiNbMoTaW. The $T_C$ vs $x$ dependence in ${\left(\mathrm{NbTaHfTiZr}\right)}_{1.0}{\mathrm{N}}_x$ exhibits a different course, in which $T_C$ first decreases from $\sim 6.5\mathrm{K}$ at $x=0$ to $T_C\approx 1\mathrm{K}$ at $x=0.25$ and $x=0.42$, and then starts to increase and reaches a maximum of $\sim 8.6\mathrm{K}$ at $x=0.81$ followed by a decline to $\sim 6.7\mathrm{K}$ when $x$ approaches the stoichiometric value 1. In this case, the transition of the initial high entropy alloy bcc structure to the fcc structure of high entropy nitrides proceeds slowly and leads to a wide $x$ range in which $T_C$ is suppressed. The analysis shows that the $T_C$ vs $x$ course and the $T_C$ enhancement in high entropy nitrides depend on the valence electron concentration of the initial high entropy alloy, as higher values accelerate the tendency to form a fcc structure and are less sensitive to the localization of otherwise mobile electrons in metallic high entropy alloys due to their bonding to N atoms. However, other parameters, such as the atomic size difference of the metallic constituents and their affinity towards nitrogen, also have to be considered.

Superionic materials have attracted considerable interest due to their unique electronic and thermal transporting properties, with far-reaching implications for solid-state electrolyte batteries and planetary science. Despite extensive studies, the physicochemical origin of superionic behavior remains insufficiently understood. In this work, we develop a generalized machine-learning descriptor for superionic materials by combining structural, elemental, and density-functional theory primary features with the Sure Independence Screening and Sparsifying Operator (sisso) framework. We identify four key factors to recognize superionic materials: electronegativity, chemical hardness, density, and bond strength. The developed machine-learning descriptor applies well beyond conventional lithium- and sodium-based superionic systems and can be extended to high-pressure conditions. Based on our machine-learning descriptor, we conducted a high-throughput screening of 13 019 materials from the materials project database, and 353 potential superionic candidates were identified. This study not only sheds light on the underlying physical origin of the superionic state but also provides guidance and insights for the design and experimental synthesis of future superionic materials.

FeS is a key end-member iron alloy relevant to the cores of telluric planets. Here, we present a comprehensive study of the FeS phase diagram up to 150 GPa and 3000 K, using in situ x-ray diffraction measurements in laser-heated diamond anvil cells. Our results extend the determination of the FeS melting curve up to 100 GPa. We have investigated the subsolidus phase relations of FeS, observing transitions between FeS-VI (MnP-type structure) and FeS-IV (distorded NiAs-type structure). We find that this transition is second-order, with the stability range of FeS-IV narrowing with increasing pressure. Additionally, we identify a novel phase, designated FeS-IX, which is formed at high temperatures above the stability field of FeS-IV, and persists up to the melting point of the alloy. By integrating our data with ambient-temperature literature results, we establish a thermal equation of state for FeS over the investigated pressure and temperature range. These findings carry significant implications for understanding the thermal state and structure of planetary cores, with specific relevance to those of Mercury and Mars.

Molecular dynamics simulations are applied to study the shock response of the hard and soft phases of nanostructured polyureas. Shocks are modeled using both a nonequilibrium explicit impact method and a quasistatic Hugoniostat method. These methods subject systems to different strain rate histories, resulting in dissimilarities in the transient evolution of the thermodynamic state of the material during shock loading. Once materials are compressed into glassy states, both Hugoniostat and impact simulations display similar Eyring-like relaxation of the residual shear stress corresponding to a logarithmic slowdown in plastic deformation post-shock. The slowly relaxing shear stress makes the prediction of post-shock densities and shock speeds sensitive to total simulation time. While Hugoniostats can efficiently resolve the steady-state limiting Hugoniot, our results indicate that this is unlikely to be realized in experiments over the timescales during which shocks transit real microstructures. Instead, real shocks will travel at transient shock speeds governed by the dynamic stress relaxation of the relevant phases, which can be predicted by explicit impact simulations.

${\mathrm{ThCr}}_2{\mathrm{Si}}_2$-type intermetallics are layered conductors in which crystallographic anisotropy and multiband electronic states often give rise to characteristic magnetotransport phenomena. Here we report the molecular-beam epitaxy growth of ${\mathrm{LaAg}}_2{\mathrm{Ge}}_2$ thin films on MgO(001) and their magnetotransport properties. Hall measurements are well described by an effective two-carrier model with a high-mobility minority electron coexisting with a low-mobility majority hole. The observed positive magnetoresistance of 22.5% at 9 T exceeds the prediction of the isotropic two-band Drude model by more than an order of magnitude, indicating an anisotropic multisheet Fermi-surface origin. Consistently, angle-dependent magnetoresistance exhibits a dominant twofold anisotropy and additional reproducible dip/peak features at characteristic tilt angles that are nearly independent of field and temperature. These results extend our understanding of the anisotropic electronic transport in thin-film germanides within the ${\mathrm{ThCr}}_2{\mathrm{Si}}_2$ family.

Magnesium (Mg) is a lightweight structural metal with high specific strength, but its limited room-temperature ductility—stemming from its hcp crystal structure—remains a major barrier to its broader engineering applications. Enhancing the plastic deformability of Mg through alloying has emerged as a promising strategy, yet the atomistic mechanisms underlying these improvements remain poorly understood. In the present work, we develop a machine learning potential (MLP) to accurately model Mg-Bi alloys and elemental Mg with quantum-level fidelity and computational efficiency. Using this MLP, we perform large-scale molecular dynamics (MD) simulations to investigate the mechanical behavior of pure Mg and Mg-5%Bi nanopillars under uniaxial compression and tension along the [0001] direction. The simulation results reveal that Bi addition (5 at %) significantly enhances Mg's plasticity by promoting the nucleation and glide of $1/2\langle \mathrm{c}+\mathrm{a}\rangle$ dislocations. This leads to a transition in the dominant deformation mechanism—from transformation-assisted plasticity in pure Mg to dislocation-dominated plasticity in Mg-5%Bi. Moreover, our simulations quantitatively reproduce the experimentally observed asymmetry in yield strength, where compressive strength exceeds tensile strength along the $c$ axis. This work not only elucidates the atomic-scale origin of ductility enhancement via Bi addition, but also reveals the importance of atomistic modeling using MLP for predicting the mechanical behaviors of complex alloy systems.

The new non-collinear magnetic order, in an Al-doped lithium ferrite (Al-LFO), $\left({\mathrm{Li}}_{0.5}{\mathrm{Al}}_{0.5}\right){\left({\mathrm{Fe}}_{0.75}{\mathrm{Li}}_{0.25}\right)}_2{\mathrm{Fe}}_3{\mathrm{O}}_8$ (denoted as Li50Al50), could be determined in the magnetic space group $\mathit{P}{4}_3{2^{\prime }}_1{2}^{\prime }$ using high-resolution neutron powder diffraction (HRNPD) at 3 and 50 K. The largest spin-canting angle of the non-collinear octahedral B-sublattice determined from the structural analysis using 3K-HRNPD approaches the Yafet-Kittel angle 21° at 0 K, extrapolated from saturation magnetization. The spin-canting textures shown at 3 and 50 K are thermally averaged at elevated temperatures to reveal collinear spin alignments along [001] at 300 K under zero external fields. The non-collinearity of magnetic spins in Al-LFOs arises from multiple spin-reorientation (SR) processes without magnetic phase transitions below $T_c$ (e.g., 788 K in Li50Al50). The SRs are activated above 100 K, showing Arrhenius behavior, but blocked at 5 K without altering the spontaneous magnetic polarization, as indicated by ac magnetic susceptibility data. The dilute effect of $\mathrm{L}{\mathrm{i}}^{+}$ replacing $\mathrm{F}{\mathrm{e}}^{3+}$ ($20\%$ in Li60Al40 or $25\%$ in Li50Al50) because of the respective $\mathrm{A}{\mathrm{l}}^{3+}$-substitution for $40\%$ and $50\%$ $\mathrm{L}{\mathrm{i}}^{+}$ in the geometrically frustrated B-sublattice (the hyperkagome lattice) enhances not only the lattice-distortion-induced electric polarization, but also the intrinsic spin dynamics. All SR-related features in both Al-LFOs are effectively quenched above 0.5 kOe, where all magnetic spins of $\mathrm{F}{\mathrm{e}}^{3+}$ are collinearly aligned parallel to the external magnetic fields, independent of frequency and temperature. These findings could be applied to further develop LFO-type multiferroics, e.g., for photovoltaic applications.

In this work, we construct a database containing approximately 30 000 entries for the frequency-dependent dielectric function within the independent-particle approximation, covering a wide range of semiconductors. Calculations are performed using the PBE and TASK approximations to the exchange-correlation potential. Building on these results, we evaluate various approaches to dimensionality reduction of the spectra, including convolutional autoencoders, which achieve effective compression to a latent space around 50 times smaller. These models are comparatively inexpensive to train and help reduce the computational cost associated with training large, off-the-shelf neural network models. The resulting models are subsequently employed to screen for wide-bandgap, high-refractive-index materials.

A rigorous understanding of the thermodynamic properties of point defects, namely vacancies and self-interstitials, is crucial for the discovery and screening of structural materials in clean energy applications. In this work, we extend a previously-developed statistical framework for predicting the thermodynamics of single-site impurities to further predict the thermodynamics of self-interstitial dumbbells in an arbitrarily complex alloy. We then apply this extended framework to compute effective formation energies in fully disordered Fe-Cr and Cu-Ni alloys. Notably, we predict that some self-interstitial dumbbell types that are high-energy in pure Fe become stabilized by Cr. We additionally describe a symmetry-breaking effect, wherein high solute concentrations distort the defect-free energy surface, yielding misaligned self-interstitials.

This work reports the electrical characteristics comparison study between ${\mathrm{Cr}}_2{\mathrm{O}}_3$ and ${\mathrm{NiO}}_{\mathrm{x}}$ based heterojunction diodes (HJD) on halide vapor phase epitaxy (HVPE) grown β-${\mathrm{Ga}}_2{\mathrm{O}}_3$ epitaxial layers. Both as-fabricated ${\mathrm{Cr}}_2{\mathrm{O}}_3$ and ${\mathrm{NiO}}_{\mathrm{x}}$ HJDs exhibited forward current density in a range of 130–150 $\mathrm{A}/{\mathrm{cm}}^2$ at 5 V with rectifying ratios $>{10}^{10}$ and a reverse leakage current density at ${10}^{-8} \mathrm{A}/{\mathrm{cm}}^2$ at $-5\mathrm{V}$. The differential specific on-resistance of ${\mathrm{Cr}}_2{\mathrm{O}}_3$ and ${\mathrm{NiO}}_{\mathrm{x}}$ HJDs was $12.01\mathrm{m}\mathrm{\Omega }{\mathrm{cm}}^2$ and $12.05\mathrm{m}\mathrm{\Omega }{\mathrm{cm}}^2$, respectively. Breakdown voltages of ${\mathrm{Cr}}_2{\mathrm{O}}_3$ HJDs ranged from 1.4–1.9 kV and 1.5–2.3 kV for ${\mathrm{NiO}}_{\mathrm{x}}$ HJDs. Theoretical band alignment between ${\mathrm{Cr}}_2{\mathrm{O}}_3$ and β-${\mathrm{Ga}}_2{\mathrm{O}}_3$ was calculated from first principles. The ambient exposed ${\mathrm{NiO}}_{\mathrm{x}}$/HVPE β-${\mathrm{Ga}}_2{\mathrm{O}}_3$ HJDs’ forward current density degraded after 10 days while that of ${\mathrm{Cr}}_2{\mathrm{O}}_3$/HVPE β-${\mathrm{Ga}}_2{\mathrm{O}}_3$ HJDs’ remained nearly unchanged after the same amount of time. It was later confirmed that the ambient exposed sputtered ${\mathrm{NiO}}_{\mathrm{x}}$ sheet resistance (${\mathrm{R}}_{\mathrm{sh}}$) degradation gave rise to the reduction of the forward current density of the ${\mathrm{NiO}}_{\mathrm{x}}$ based HJDs, and water (${\mathrm{H}}_2\mathrm{O}$) was qualitatively determined to be the agent attributed to the forward conduction degradation by measuring the ${\mathrm{R}}_{\mathrm{sh}}$ of ${\mathrm{NiO}}_{\mathrm{x}}$-on-sapphire reference wafer after exposing it to different environments. The ${\mathrm{Cr}}_2{\mathrm{O}}_3$/HVPE β-${\mathrm{Ga}}_2{\mathrm{O}}_3$ HJD also exhibited enhanced thermal stability compared to the ${\mathrm{NiO}}_{\mathrm{x}}$/β-${\mathrm{Ga}}_2{\mathrm{O}}_3$ heterostructures at elevated temperatures.

Emphanisis-induced polaron relaxation mechanism and local piezoelectricity are examined in $\mathrm{C}{\mathrm{s}}_2\mathrm{NaBiC}{\mathrm{l}}_6$ and $\mathrm{C}{\mathrm{s}}_2\mathrm{AgBiC}{\mathrm{l}}_6$ double perovskites, wherein stereochemically active bismuth $6s^2$ lone pairs account for dynamic off-centering. Nonlinear thermal expansion from temperature-dependent x-ray diffraction and systematic blueshift of the Raman modes compared with harmonic predictions establish notable anharmonicity, while mean square deviation of bismuth atoms according to molecular-dynamics trajectory and Bi–Cl bond-length asymmetry in x-ray absorption fine structure directly validate emphanisis. Dielectric and ac conductivity dispersions confirm non-Debye relaxation and overlapping large-polaron tunneling mechanism, where the pronounced charge-phonon coupling rationalizes the polaron radius as a viable electrical probe of lattice dynamical disorder. Piezoresponse force microscopy confirms reversible local piezoelectricity, originating from the emphanisis-driven local symmetry breaking in these globally centrosymmetric $\mathrm{C}{\mathrm{s}}_2\mathrm{NaBiC}{\mathrm{l}}_6$ and $\mathrm{C}{\mathrm{s}}_2\mathrm{AgBiC}{\mathrm{l}}_6$ lattices. Embedding these perovskites into polyvinylidene fluoride promotes electroactive $\beta$-phase nucleation via localized electromechanical coupling and produces nanocomposites with enhanced piezoelectric output, strain sensitivity, and durability. First-principles calculations attribute the superior performance of $\mathrm{C}{\mathrm{s}}_2\mathrm{NaBiC}{\mathrm{l}}_6$-based composites to stronger interfacial bonding and greater charge transfer compared with the Ag-based analog. The synergy of robust polaron dynamics, high piezoelectric coefficient, and optimized interfacial electronic structure supports the exceptional potential of $\mathrm{C}{\mathrm{s}}_2\mathrm{NaBiC}{\mathrm{l}}_6\text{−}\mathrm{PVDF}$ nanogenerators. Our convergent experimental-theoretical approach examines emphanisis spectroscopically and establishes it as a critical alterable design principle to activate electromechanical functionality via functional fillers in otherwise nonpolar solids, and thereby enables compact, sustainable, on-chip energy harvesting.

The magnetic history of extraterrestrial materials, such as meteorites, is a critical archive for understanding solar system processes. However, the effect of hypervelocity collisions on this record remains poorly understood, particularly whether such events can erase or reset magnetization through heating or pressure-induced phase transformations. Using spin-lattice dynamics simulations, we investigate collisions between nanoscale iron particles (10–20 nm diameter) at velocities of 1–2 km ${\mathrm{s}}^{-1}$, explicitly modeling magnetic interactions. Our results show that while collisions at 2 km ${\mathrm{s}}^{-1}$ generate pressures sufficient to induce local melting and a limited, transient nonmagnetic hexagonal close-packed (hcp) phase, the primary magnetic effect is global heating above the Curie temperature, transitioning the particles to a paramagnetic state. The particles form a single nanoparticle after the impact, with some twins, dislocations, and point defects. Unlike under bulk single-crystal loading, several nanograins are formed. Upon simulated cooling, emulating radiative cooling, the now-joined particles consistently recover a strong, single-domain ferromagnetic state, irrespective of their initial magnetic-domain orientation or the resulting microstructural defects. The final ferromagnetic state does not preserve a memory of the pre-impact magnetic configuration. These findings demonstrate that a strong ferromagnetic signature in recovered nanoscale iron does not preclude a history of severe hypervelocity collisions, with significant implications for the interpretation of magnetic records in asteroidal and meteoritic materials.