We investigated the properties of magnetoactive cholesteric liquid crystals (CLCs) being in external static magnetic field directed along the helix axis in the case of light oblique incidence. We showed that at oblique light incidence complex band structure is observed in the first-order reflection band. In this case there appear two new photonic band gaps (PBGs). The frequencies of these new regions and their frequency widths in significant intervals can be tuned by changing the external magnetic field and the angle of incidence. The polarization of reflected light in these regions can be tuned, too: we can obtain light with right circular polarization instead of left circular polarization light or vice versa by reversing the direction of the external magnetic field. This system is nonreciprocal and the nonreciprocity changes over a wide range. This system can operate as a tunable optical diode for both orthogonal circular and orthogonal linear polarizations. We investigated the features of the wave vectors of Bloch waves excited in magnetoactive CLCs in an external magnetic field with the direction of light propagation oblique with respect to the helix axis. We showed that new Dirac points appear on both sides of the main PBG. And it is at these Dirac points that new PBGs appear. We investigated the light localization peculiarities in this structure too.

Two-dimensional (2D) ferromagnetic topological materials (FMTMs), capable of integrating spin-polarized conduction and nontrivial quantum states, are pivotal for advancing spintronic and topological microelectronics. However, existing 2D FMTMs face a critical trade-off between robust quantum phenomena (e.g., quantum anomalous Hall effect, QAHE) and optical transparency. Here, we demonstrate through first-principles calculations that a Mo-doped LiMgAs monolayer $\left({\mathrm{Li}}_{12}{\mathrm{Mg}}_{10}{\mathrm{Mo}}_2{\mathrm{As}}_{12}\right)$ breaks this limitation by synergizing the groundbreaking features: (1) strain-robust Weyl half-semimetallicity with fully spin-polarized Weyl points near the Fermi level, stable under −5%–5% biaxial strain; (2) topological phase transition to QAHE via spin-orbit coupling (SOC), yielding a Chern number C = +1 and quantum anomalous Hall effect; and (3) unprecedented optical transparency (without SOC) exceeding 90% in the visible spectrum, outperforming conventional 2D magnetic systems. Remarkably, the ${\mathrm{Li}}_{12}{\mathrm{Mg}}_{10}{\mathrm{Mo}}_2{\mathrm{As}}_{12}$ monolayer maintains room-temperature-compatible thermal stability (300 K ab initio molecular dynamics simulations) and a much higher Curie temperature $(T_{\mathrm{C}}=178 \mathrm{K})$. This multifunctional integration of half-metallic ferromagnetism, topology-switching capability, and ultrahigh transparency positions ${\mathrm{Li}}_{12}{\mathrm{Mg}}_{10}{\mathrm{Mo}}_2{\mathrm{As}}_{12}$ as a promising material for designing transparent quantum Hall sensors, low-power spin filters, and wearable optoelectronic devices, thereby bridging quantum topology with photonic technology.

The anisotropy of interface energy, alongside coherency strain energy, is crucial in determining precipitate morphology and interface instabilities in superalloys. However, most experiments and mesoscale simulations assume isotropic interface energy, although the interface energy anisotropy is significant in Ni-based superalloys. While atomistic simulations have progressed, the whole orientation space of the coherent face-centered-$\mathrm{cubic}/\mathrm{L}{1}_2$ interface remains unexplored, especially for low-symmetry interface plane orientations. In the present work, we investigate the full interface plane orientation space of coherent interfaces of a binary Ni-based superalloy ($\mathrm{Ni}\text{/}{\mathrm{Ni}}_3\mathrm{Al}$) using molecular dynamics simulations, determining the full interface energy anisotropy. The unprecedented orientation resolution allows the identification of structural and energetic details, which can build the basis for identifying structural building blocks (step lines) explaining interface energy anisotropy. We propose a step-structure model of coherent interfaces and apply it to predict the interface energy anisotropy based on noninteracting steps on facets.

Magnetic MAX phase compounds are important materials for studying the two-dimensional magnetism because of their layered crystallographic structure. The hexagonal MAX phase compound ${\mathrm{Cr}}_2\mathrm{GeC}$ is a Pauli paramagnet, and here we report the induction of an ordered magnetic state by doping Fe at the Cr site. Induced magnetism for small doping concentrations (indicated as 5% and 2.5%) is found to have a weak itinerant ferromagnetic character. The Rhodes-Wohlfarth ratio is found to be 13.29, while the coefficient of electronic heat capacity ($\mathrm{\Gamma }$) is 27 mJ-${\mathrm{mol}}^{-1}{\mathrm{K}}^{-2}$ for ${\mathrm{Cr}}_{1.9}{\mathrm{Fe}}_{0.1}\mathrm{GeC}$. Our x-ray magnetic circular dichorism measurement confirms that the magnetic moment arises from the Fe atom only, and Cr has negligible contribution towards the ordered moment. Our critical analysis indicates that the magnetic phase transition in ${\mathrm{Cr}}_{1.9}{\mathrm{Fe}}_{0.1}\mathrm{GeC}$ follows mean field theory.

We present a comprehensive investigation of the field-dependent critical current density and pinning force, combined with a detailed analysis of the nanostructural defect landscape in single crystal of underdoped PrFeAs(O,F) superconductor. Our study demonstrates that for both in-plane and out-of-plane magnetic field orientations, critical current density exhibits a strong pinning regime in intermediate fields across the entire temperature range. The dominant contribution to pinning originates from oxygen-to-fluorine substitutional defects, oxygen vacancies, which all act as point defects via a quasiparticle mean free path fluctuation mechanism. Scanning transmission electron microscope studies did not reveal any volume or surface defect types within the lattice.

Extended x-ray absorption fine structure (EXAFS) measurements of single-crystal Ge/GeSn radial heterostructure nanowires are used to examine the effects of composition on both short-range order (SRO) and longer-range disorder in GeSn alloys. GeSn has prompted significant interest because it can achieve a direct band gap for sufficient Sn concentrations beyond the equilibrium solid solubility limit in an all-group IV system. Short-range order in this material is particularly interesting as it has been predicted to affect the band gap independent of average composition or strain effects. By independently controlling the Sn composition and GeSn thickness during chemical vapor deposition of misfitting GeSn shells around ultrathin, elastically compliant, Ge core nanowires, the elastic misfit strain in the GeSn is minimized for Sn compositions over the studied range $\approx \mathrm{G}{\mathrm{e}}_{0.96}\mathrm{S}{\mathrm{n}}_{0.04}$ to $\mathrm{G}{\mathrm{e}}_{0.88}\mathrm{S}{\mathrm{n}}_{0.12}$. The degree of SRO was found to decrease with increasing Sn composition. Additionally, damping of the EXAFS signal was observed as the Sn content increased, particularly for increasingly distant atomic shells about the absorbing atom, even for scattering paths not involving Sn atoms. This result is quantified as an increase in the mean-squared relative displacement parameters of the shells. These measurements reveal the accommodation of local strain due to the presence of the highly size-mismatched Sn atoms in the Ge diamond cubic lattice ($\approx 14\%$), which may have effects on the band structure of the material in addition to the influence of short-range atomic order. Comparison among the nanowire samples allows for calculation of the topological rigidity parameter, $a^{**}$, for the first-neighbor bond lengths. These exhibit chemically distinct values for Ge-Ge, Ge-Sn, and Sn-Sn, and they are consistent with the value $a^{**}=0.75\pm 0.07$ confirming the general applicability of the model to alloys with both large amounts of natural misfit strain and the potential for short-range order.

Iridium-containing conducting materials are widely investigated for their strong spin-orbit coupling and potential topological properties. Recently the commonly used electrode material iridium dioxide was found to host a large spin-Hall conductivity and was shown to support Dirac nodal lines. Here we present quantum-oscillation experiments on high-quality ${\mathrm{IrO}}_2$ single crystals using the de Haas-van Alphen effect measured using torque magnetometry with a piezoresistive microcantilever as well as density functional theory-based band-structure calculations. The angle, temperature, and field dependencies of the oscillations and the calculated band dispersion provide valuable information on the properties of the charge carriers, including the Fermi-surface geometry and electronic correlations. Comparison of experimental results to calculations allows us to assigns the observed de Haas-van Alphen frequencies to the calculated Fermi surface topology. We find that the effective masses of ${\mathrm{IrO}}_2$ are enhanced compared to the rest electron mass $m_e$, ranging from 1.9 to 3.0 $m_e$, whereas the scattering times indicate excellent sample quality. We discuss our results in context with recent ARPES and band-structure calculation results that found Dirac nodal lines in ${\mathrm{IrO}}_2$ and compare the effective masses and other electronic properties to those of similar materials like the nodal chain metal ${\mathrm{ReO}}_2$ in which Dirac electrons with very light effective masses have been observed.

An integrated data-driven approach combined with a high-throughput framework based on first-principles calculations was employed to discover novel rare-earth-free permanent magnets, focusing on binary alloys. Compounds were systematically screened based on their elemental composition, structure, stability, and magnetization. Density functional theory (DFT) calculations were performed on selected candidates to evaluate their magnetocrystalline anisotropy energy and Curie temperature ($T_{\mathrm{C}}$), leading to the identification of 10 promising materials. Out of these, a thorough literature review confirmed the novelty of ZnFe, while ${\mathrm{Fe}}_8\mathrm{N}$ corresponds to the well-known ${\mathrm{Fe}}_{16}{\mathrm{N}}_2$ phase, extensively investigated in thin-film form, but with limited data available for its bulk counterpart. Our computational analysis addresses this gap by providing valuable insight into its bulk magnetic properties, thereby supporting its continued relevance as a high-performance rare-earth-free magnet and reinforcing the effectiveness of our screening strategy. Their ferromagnetic ground state was verified via DFT, and structural stability confirmed through negative formation enthalpies, phonon spectra, and elastic criteria. Tetragonal ZnFe and ${\mathrm{Fe}}_8\mathrm{N}$ exhibit high saturation magnetization ($>1\mathrm{T}$), large anisotropy constants ($>0.5\text{MJ}/{\mathrm{m}}^3$), and high $T_{\mathrm{C}}$ ($>1200\mathrm{K}$). Their magnetic hardness parameters ($\kappa$ = 0.85 for ZnFe and 0.70 for ${\mathrm{Fe}}_8\mathrm{N}$) further support their potential as gap magnets. These findings underscore the effectiveness of our high-throughput screening strategy, offering a theoretical blueprint for the experimental realization of rare-earth-free permanent magnets.

Because heterostructures have a layered structure, a large surface area, and several accommodating sites, they efficiently maximize the characteristics of rechargeable Li-ion batteries (LIBs). Based on density functional theory calculations, the electrochemical, electronic, diffusion, adsorption, and mechanical properties of InSnPS/GaGeAsSe heterostructure as anode material for LIB are investigated in this work. The predicted 2D heterostructure has a mechanically and dynamically stable structure with a small lattice mismatch (2.92%). The InSnPS/GaGeAsSe effectively isolates the electrons and holes at the interface by creating a staggered type II band alignment, extending the carrier lifetime. Additionally, the InSnPS/GaGeAsSe heterostructure has low average open circuit voltages of 0.69 V and a storage capacity of $483.38\mathrm{mAh}{\mathrm{g}}^{–1}$ because of its energetically advantageous adsorption of five layers of Li atoms. The remarkable charge–discharge capabilities of the InSnPS/GaGeAsSe are demonstrated by the low activation barrier of 0.23 eV, which illustrates the quicker mobility of Li ions. Considering the high theoretical specific capacities, low diffusion energy barriers, strong adsorption properties, structural integrity and low open circuit voltages, the InSnPS/GaGeAsSe heterostructure is predicted to be the preferable anode material for LIBs.

We present a comprehensive ab initio dataset of formation energies and elastic properties of intrinsic point defects across all the transition and rare earth hexagonal close packed (hcp) metals, as well as metalloid elements with hcp crystal structure. Point defect properties appear weakly correlated with the $c/a$ ratio of the hcp lattice. Instead, it is the position of an element in the Periodic Table that primarily defines the relaxation volume tensor, elastic dipole tensor, and formation energy of a point defect. This suggests that the local variations in the electronic structure and interatomic bonding at the core of a defect dominate its properties, as opposed to long-range elastic deformations of the lattice. Across all the metals, we find that the relaxation volumes of vacancies and self-interstitial defects are correlated with atomic volumes, with values of −0.35 and 1.46 atomic volumes for a vacancy and a self-interstitial defect, respectively, providing a universally good approximation independent of the crystal structure. This study complements and completes the existing point defect databases spanning body-centered cubic and face-centered cubic metals.

In this study, we investigate the formation of electron and hole small polarons in the prototypical ferroelectric material ${\mathrm{BaTiO}}_3$, with a focus on their interaction with ferroelectric distortive fields. To accurately describe the ferroelectric phase in electronically correlated ${\mathrm{BaTiO}}_3$, we employ the HSE06 hybrid density functional, which addresses the limitations of conventional density-functional theory (DFT) and Hubbard-corrected $\mathrm{DFT}+\mathrm{U}$ models, providing a more precise depiction of both ferroelectric and polaronic behaviors. Our analysis spans three structural phases of ${\mathrm{BaTiO}}_3$: cubic, tetragonal, and rhombohedral. We uncover a unique phase-dependent trend in electron-polaron stability, which progressively increases across the structural phases, peaking in the rhombohedral phase due to the constructive coupling between the polaron and ferroelectric phonon fields. In contrast, hole polarons exhibit a stability pattern largely unaffected by the phase transitions. Furthermore, we observe that polaron self-trapping significantly alters the local ferroelectric distortive pattern, which propagates to neighboring sites but has a minimal effect on the long-range macroscopic spontaneous polarization. Charge trapping is also associated with localized spin formation, opening new possibilities for enhanced functionalities in multiferroic materials.

Twisted two-dimensional materials have emerged as a topic of high current interest in condensed-matter physics since the breakthrough of the twisted bilayer graphene. In this work, the structural and electronic properties, including the out-of-plane polarization of large (336 atoms) twisted hexagonal boron nitride flakes on graphene are investigated on the basis of density-functional theory calculations. Eleven different twist angles are examined, ranging from $0^{\text{o}}$ to ${60}^{\text{o}}$. The variation in the binding energies as a function of rotation angles is insignificant, suggesting a weak barrier for hBN-flake rotation. Additionally, the results demonstrate that the presence of the large hBN-flake breaks the symmetry of pristine graphene and opens a band gap. The largest value of the band gap is found to be 14.3 meV for $0^{\text{o}}$ twist angle. By investigating the vertical distance of the individual atoms in the flake to graphene, we find that it is laterally modulated where shorter distances exhibit an associated charge accumulation. Bader charge values show that the electron charge moves from graphene to the hBN flake, giving rise to a negative out-of-plane polarization that points downward from the hBN flake to graphene, where there is a 0.20 pC/m difference between twisted and nontwisted ($0^{\text{o}}$) configurations. The highest occupied and lowest unoccupied molecular orbitals are delocalized on graphene, but show a striking difference in shape and symmetry that reflects their interaction with the flake, where the former are of bonding character and the latter antibonding. The present results show that the twist angle can be used as an additional degree of freedom to tune the electronic properties of hBN flakes on graphene, which may be utilized in future electronic devices.

$\beta \text{−}{\mathrm{Ga}}_2{\mathrm{O}}_3$ is a promising material for next-generation power electronics because of its ultrawide band gap and high critical breakdown voltage. However, realizing its full potential requires precise control over dopant incorporation and stability. In this work, we use first-principles calculations to systematically assess the diffusion behavior of eight potential deep-level substitutional acceptors (Au, Ca, Co, Cu, Fe, Mg, Mn, and Ni) in $\beta \text{−}{\mathrm{Ga}}_2{\mathrm{O}}_3$. We consider two key diffusion mechanisms: (i) interstitial diffusion under nonequilibrium conditions relevant to ion implantation, and (ii) trap-limited diffusion (TLD) under near-equilibrium thermal annealing conditions. Our results reveal a strong diffusion anisotropy along the $b$ and $c$ axes, with dopant behavior governed by competition between diffusion and incorporation (or dissociation) activation energies. Under interstitial diffusion, ${\mathrm{Ca}}_{\text{i}}^{2+}$ and ${\mathrm{Mg}}_{\text{i}}^{2+}$ show the most favorable combination of low migration and incorporation barriers, making them promising candidates for efficient doping along the $b$ and $c$ axes, respectively. In contrast, ${\mathrm{Au}}_{\text{i}}^{+}$ diffuses readily, but exhibits an incorporation barrier that exceeds 5 eV, rendering it ineffective as a dopant. From a thermal stability perspective, ${\mathrm{Co}}_{\text{i}}^{2+}$ shows poor activation but high diffusion barriers, which may suppress undesirable migration at elevated temperatures. Under trap-limited diffusion, the dissociation of dopant-host complexes controls mobility. ${\mathrm{Mg}}_{\text{i}}^{2+}$ again emerges as a leading candidate, exhibiting the lowest dissociation barriers along both axes, whereas ${\mathrm{Co}}_{\text{i}}^{2+}$ and ${\mathrm{Fe}}_{\text{i}}^{2+}$ display the highest barriers, suggesting improved dopant retention under thermal stress. Our findings guide dopant selection by balancing activation and thermal stability, essential for robust semi-insulating substrates.

Recently, well-crystallized and nearly phase-pure Lonsdaleite (hexagonal diamond) has been successfully synthesized by heating graphite under extreme pressure conditions. Despite ongoing investigations into its physical properties, there remains a lack of high-precision interatomic potentials capable of accurately capturing its thermal transport behavior. In this work, we constructed a high performance Neuroevolution potential (NEP) model for hexagonal diamond, trained on a data-set generated via ab initio molecular dynamics (AIMD) simulations. The accuracy of the NEP model was assessed by comparing phonon dispersion curves derived from the NEP and density functional theory (DFT) calculations, revealing excellent agreement. The vibration modes and phonon irreducible representation of hexagonal diamond at the Γ point were further analyzed. The Raman active modes include ${\mathrm{A}}_{1\mathrm{g}}, {\mathrm{E}}_{1\mathrm{g}}$, and ${\mathrm{E}}_{2\mathrm{g}}$, and the infrared active modes include ${\mathrm{A}}_{2\mathrm{u}}$ and ${\mathrm{E}}_{1\mathrm{u}}$. Subsequently, the lattice thermal conductivity of hexagonal diamond was calculated, with a particular focus on the modal contributions. A comprehensive analysis of temperature-dependent thermal conductivity in the range of 300–3000 K shows that the thermal conductivity decreases with increasing temperature. This trend is primarily attributed to increased phonon-phonon anharmonic scattering at elevated temperatures. Moreover, comparative analysis indicated that the thermal conductivity of hexagonal diamond is lower than that of diamond, which can be ascribed to enhanced acoustic-optical phonon scattering in the hexagonal lattice. These findings provide in-depth theoretical insights into the phonon transport characteristics of hexagonal diamond.

Understanding interfacial thermal transport is essential for improving thermal management in high-speed power electronic devices, where the efficient removal of excess heat is a critical challenge. In this study, a machine-learning interatomic potential with near-first-principles accuracy was employed to investigate the interfacial thermal conductance (ITC) between [111]-oriented cubic boron arsenide (cBAs) and [0001]-oriented 4H silicon carbide (4H-SiC), as well as its dependence on uniaxial stress. Among all possible bonding configurations at the cBAs(111)/4H-SiC(0001) interface, the B–C bonded interface was identified as the most energetically favorable. Nonequilibrium molecular-dynamics simulations revealed that, under ambient conditions (300 K and 0 GPa), the ITC of the B–C interface reaches $353\pm 6\mathrm{MW}{\mathrm{m}}^{-2}{\mathrm{K}}^{-1}$, and increases monotonically to $460\pm 3\mathrm{MW}{\mathrm{m}}^{-2}{\mathrm{K}}^{-1}$ under a uniaxial stress of 25 GPa perpendicular to the interface. For comparison, the As–C-bonded interface exhibits a lower ITC, increasing from $233\pm 7$ to $318\pm 6\mathrm{MW}{\mathrm{m}}^{-2}{\mathrm{K}}^{-1}$ over the same stress range. These results demonstrate that proper interfacial bonding and moderate uniaxial stress can significantly enhance thermal transport across the cBAs(111)/4H-SiC(0001) heterointerface, offering valuable insight for thermal design in next-generation power electronics.